|"The person who stole that stuff was the old me. Once I got airbending, I changed. I don't know how to explain it, but I feel like airbending chose me for a reason, like I'm a new person."|
|— Kai to Korra.|
Kai is an orphan who became an airbender after the Harmonic Convergence of 171 AG. He was a mischievous thief who was eventually caught by the Dai Li in Ba Sing Se for using airbending, but was later liberated from their control and went with Tenzin and the other new airbenders to train his skills and learn Air Nomad culture at the Northern Air Temple. As part of the Air Nation, he became a more honorable person, living to serve others by bringing peace and balance wherever possible. Sometime after 171 AG, he also entered in a romantic relationship with Jinora.
Kai grew up as an orphan. When he was finally adopted by a nice family in 170 AG, he took advantage of their kindness by stealing their life savings and spent six months on the run from Earth Kingdom authorities.
Joining Team Avatar
Following Harmonic Convergence, Kai soon discovered he possessed airbending. Soon after, he encountered Team Avatar, who was searching for airbenders to rebuild the Air Nation. He told them a false story on how his parents were killed by outlaws who were pursuing them, earning their sympathy and quickly being accepted in their company. Just as he boarded their airship, ready to depart, a sheriff and his deputies arrived, whom he falsely claimed to be outlaws. After Avatar Korra bested them, the sheriff revealed Kai's true identity as a thief. The boy attempted to run off with his loot, but was caught by Mako. The sheriff quickly took custody of the young lad, intending to send him to prison. However, in exchange for returning the life savings to Kai's family, Korra convinced the sheriff to allow Kai to turn over a new leaf with Team Avatar. Though the compromise was accepted, Mako warned Kai that he would be watching him, stating he knew the kind of person Kai was, due to having a similar past. Promising to change, the young boy turned to board the ship, where he gladly accepted Jinora's offer to teach him more about airbending, just before she blushed.
Ba Sing Se
While en route to Ba Sing Se, Kai attended an airbending lesson under Jinora's tutelage, during which he swiftly took down Bumi with one air swipe. He stole the retired commander's wallet during the skirmish, engaging in a game of chase after Bumi found out.
Upon arriving in Ba Sing Se, Kai's kleptomania got the better of him and he slipped away to use his airbending to pickpocket the wealthy. When the team noticed his absence, Kai was found by Mako and Bolin while he robbed a rich Ba Sing Se citizen. He ran away from them, though as he boarded the monorail, he was grabbed by the collar by Mako. However, he used his airbending to free himself and managed to exit the cart just in time before it left for the Lower Ring, leaving the brothers on it without their wallets.
That night, he used his loot to settle down in a luxury resort, where he was addressed as "Master Fong". The following day, he resumed his scam to rob more citizens, though by nightfall, he was cornered by two Dai Li agents in a small alley. Although he tried to make a run for it, he was captured by their rock gloves and subsequently thrown in prison with other airbenders, where he was notified that he had been conscripted in Earth Queen Hou-Ting's first airbending regiment.
Later, Kai was pitted against Yung, one of the other airbenders, during a training session and was chastised by his Dai Li overseer for holding back. Kai responded by attacking with a stronger air blast, but apologized when his attack knocked Yung to the ground, only to be chastised once again. When the session turned to defense against earth projectiles, Kai proved more adept than the others, blocking every attack launched at him. After Kai protected Yung from being hit by projectiles, the overseer began to attack him more furiously until he eventually knocked the young airbender to the floor. Kai retaliated with an airblast, which his opponent evaded and punished the boy for his insolence by throwing him in a cell known as "The Hole". Shortly afterward, Jinora's projected spirit appeared before him, having focused on his energies to find his location so she and Team Avatar could rescue him and the others.
Later that night, Mako, Bolin, and Jinora located and freed Kai from his prison cell. Jinora first greeted him with a kiss on the cheek, causing Kai to blush. He then faced disapproving glares from Mako and Bolin, prompting him to thank them for coming to save him and apologize for everything he had done to them. Bolin quickly forgave him with a hug, though Mako complained about the loss of his money. As the foursome attempted to leave, they were confronted by a trio of Dai Li agents, among them the overseer, who declared that Kai's desertion was punishable by death. Though Bolin was able to down two Dai Li agents, the overseer grabbed Jinora, though Kai saved her and defeated the overseer using airbending. They then escaped the Earth Queen's temple, before Bolin catapulted them onto Oogi. Once they had left Ba Sing Se, Kai joined the other airbenders in following Tenzin to the Northern Air Temple.
Northern Air Temple
After arriving at the Northern Air Temple, Kai dozed off during Tenzin's lecture about Monk Tang Xu, though woke up and laughed as Bumi mocked Tenzin's lesson. He later watched in amazement as Tenzin performed several tricks on Oogi and asked when they could fly around as such on their own bison, but was disappointed to learn many years of training were required. He also asked if they could ride a passing wild herd, but got the same answer. When the airbenders from Air Temple Island arrived, Kai joined the others in going over to greet them.
Later, Kai and Jinora watched the wild herd of bison fly by. Kai was fascinated by the animals, calling them "bisons". Tenzin attempted to correct Kai's grammar, but Kai continued to refer to multiple animals as "bisons". Kai suggested going down to ride the bison, convincing Jinora by explaining that no one was around and they could get back before anyone spotted them. Using their gliders to fly down, they saw some calves. Kai wondered why they were not flying and was told by Jinora they could not do so for their first couple weeks of life. Kai decided to sweep down and pet one of the baby bison despite Jinora's warnings about their mothers being protective. He was soon confronted by the calves' mother, who charged him, but was saved at the last second when Jinora quickly swept in on her glider and pulled him out of the bison's path. After the two settled, Kai told Jinora she was an incredible airbender and wondered why she did not have her tattoos. Jinora replied that her father did not believe she was a master yet, but Kai continued to be encouraging, stating that she could do everything her dad could in addition to having spiritual powers, thus making her a master.
The next morning, Kai and his fellow recruits were suddenly awoken by Tenzin, who led them on a ten-mile hike. Kai was the first to finish behind Tenzin and Jinora, but was left exhausted as a result of the exercise. After meditation, a sleepy Kai followed the group to a balancing exercise. Later, as Tenzin told them about shaving their heads, Kai sneaked over to Jinora, asking her if she wanted to see the baby bison again, but was shushed and advised to pay attention, prompting him to shrug and walk away. Upon being asked if he wanted his head shaved, Kai joined the rest of the group in disagreement, and they made their way to the obstacle course.
The young airbender made his way through most of the obstacles safely until the rash cacti, where he collided with Yung on a post and fell into the plants. Ultimately, he completed the course, but was left exhausted and mud-covered. He remarked what Tenzin was doing was just as bad as what the Earth Queen's prison was like. He also sneaked quietly under the crowd when Jinora told her father about his suggestion that she could get her tattoos, which irritated Tenzin.
Kai found Jinora at a temple overlook where he apologized to her. Jinora assured him that Tenzin's outburst was not his fault while lamenting her father's lack of belief in her. At Kai's suggestion, they returned to the forest, but realized neither spirits nor bison were to be found. They soon found themselves captured by bison rustlers and taken to their camp. Kai listened in fear as their leader, Ganbat, declared they would be sent to Ba Sing Se with the baby bison. With the two locked in separate cages on a truck, he suggested she try using her spiritual projection technique; ultimately, she instead had one of the spirits send a message about the danger they faced.
Kai soon got himself out by picking the lock on his cage and went to free Jinora, but she told him to free the bison first. He was soon grabbed by a rustler, but kicked up a blast of air to free himself. At that moment, the rest of the airbenders, led by Bumi, swarmed the camp and attacked the rustlers. Kai's attack failed and he was knocked down by a rock wall. He recovered just in time to keep pursuit on his glider as Ganbat fled with the truck full of bison calves and Jinora. Kai got up alongside the truck and used his bending to jump in through the open window on the driver's side, but he was grabbed and held down by Ganbat. At that point, however, Tenzin arrived on Oogi and two other adult sky bison; he successfully pulled Kai over to him. After Ganbat's truck was toppled by a bison, Kai attacked the defenseless man with an arc of air, slamming him into his truck's hood twice as payback, but Tenzin stopped him, telling him an airbender should not attack a defenseless opponent. Nevertheless, Kai was complimented on his technique by the master.
That evening, Kai and Jinora happily played with an adult bison. Tenzin approached them, saying the bison warmed up to them because they recognized their own kind. The young boy soon caught sight of the calves taking flight, excitingly telling Jinora to look.
Ambushed by the Red Lotus
When the Red Lotus arrived at the Northern Air Temple, Kai warned a group of airbenders that they needed to evacuate, but before reaching the temple's interior, Ghazan blocked their path with his lavabending, causing them to leap backward. Kai and the rest of the airbenders were soon gathered into a courtyard, where they were told by Zaheer that the Red Lotus wanted nothing, rather, they were being used as leverage for Korra; they would get away safe as long as they cooperated. While Tenzin and his siblings held Zaheer, Ghazan, and Ming-Hua off, Kai and the rest of the airbenders were told by Tenzin to head to the bison stable and stay out of P'Li's line of sight because of her combustion attacks.
The airbenders, along with Pema and Rohan, made their way down a hallway, but they were stuck near the stables because of the threat posed by P'Li, whose attacks continuously blocked their path. Kai decided to distract her to allow everyone else to escape. He used his glider to fly in the vicinity of the Red Lotus' airship while dodging P'Li's blasts. Kai was even able to hit her with an air blast, causing one of her shots to deflect off-target. However, while trying to shield himself from another beam, Kai was hit, sending him flying down the mountain in smoke. The young airbender fell into a small tree and was knocked unconscious, but he was woken up by a baby bison whom he named Lefty, who licked his face. Kai mounted the calf and, upon commanding the baby, flew back to the temple in an attempt to sneak back in to rescue the others. However, the moment he arrived, he saw an airship leaving the temple and followed it toward some Air Nomad caves a few miles away, where P'Li handed over her captives to several Red Lotus sentries. Realizing he could not fight them all, he returned to the temple, hoping Team Avatar and other reinforcements would appear to help them.
As he made it back to the temple, Kai witnessed how Bolin created a hole in the side of the mountain for him, Mako, Asami, and Tenzin to escape the incoming lava. Finding them trapped, he offered to give everyone a lift to safety on Lefty. They regrouped with the rest of Team Avatar and Suyin's forces at the base of Laghima's Peak. Although Kai was dismissed a few times, he managed to get through to the adults and reveal the airbenders' location to them all, to which they asked him why he had not mentioned it to them sooner, much to his annoyance. As he mounted his bison to lead everyone to the impromptu prison, he was approached by Mako, who apologized for his earlier skeptical behavior toward Kai. The young airbender readily accepted the apology, smiling it away by stating that he probably deserved it, to which Mako agreed.
Leading the rescue party toward the caves, Kai was reunited with a relieved Jinora, who excitedly hugged him. He exited the caves and witnessed Korra's battle with Zaheer. As she was struggling with fighting both the poison coursing through her veins and the Red Lotus' leader, he offered to fly up on his bison to help her, though his suggestion was shot down by Lin, who stated that he would never be able to keep up with Zaheer's power. Upon Jinora's instance, he and the other airbenders followed her to form a circle and together they bent a powerful tornado, which enabled Korra to bring Zaheer down.
Two weeks later, Kai had returned with everyone to Air Temple Island and he was present at Jinora's anointment ceremony as an airbending master. Upon Tenzin's sign, he and the other new airbenders bent the incense behind them and used the scented air to jingle the wind chimes in honor of the new master.
Over the next three years, Kai worked with the Air Nation to bring peace and protection where they were needed in the chaotic Earth Kingdom. He also began a romantic relationship with Jinora. One day in 174 AG, he and Opal were ordered by Tenzin to help out the state of Yi. As they reached the state's capital city on Lefty, they noticed a robbery was in progress. Without hesitation, Kai and Opal jumped off the bison and soared down, using their wingsuits. Kai easily bypassed the bandits' jeep and flipped it over by aiming a powerful gust of air at the hood, ejecting the three passengers. After Opal made sure the bandits landed safely, Kai tied them up and announced to the townspeople that it was safe to leave their homes as the airbenders were there to protect them. When the governor of the state greeted them and asked where the others were, Kai took offense and stated that Opal and himself effectively took care of three bandits already, only to be told there were hundreds more.
Upon noticing the arrival of a train to the town, Kai and Opal checked it out, hoping the vehicle carried food and other supplies. Recognizing Bolin among the people that embarked the train, Kai asked Opal what her boyfriend was doing there, receiving the answer that he must have traveled there with Kuvira and Baatar Jr., which predicted nothing good. Kai called out to Bolin, running over to him and hugging him tightly. Noticing his friend's new hairstyle, Kai remarked it made him look like a stiff. However, after Kuvira, Baatar Jr., and Opal joined them, the atmosphere grew awkward and tense and Kai distanced himself a bit from the group.
While Kuvira and the governor had a private conversation, Kai remained outside with Opal and Bolin, though when Kuvira gave the orders for departure after failing to strike a deal with the governor, Kai asked if they really were not staying to help. In response, he was handed the contract containing Kuvira's terms of agreement and told he had one day to convince the governor to sign it before the army left. As the train left for the state border, Kai proposed to use Lefty to fly to all nearby villages to pick up supplies for the people.
Kai and Opal were able to collect enough supplies for the people of the capital to feed them until they were able to find reinforcements. On their journey back, he asked how Opal and Bolin were doing. When she said she was angered about him working with Kuvira, he pointed out that it did seem that the earthbender had found his calling as he loved helping people. Upon being asked about his own relationship with Jinora, he said they were doing fine, though their conversation was cut short when a biplane, piloted by bandits, hooked their supplies by aiming a grappling gun at the net covering the food. As one of the bandits ziplined down to cut loose the tethers tying the products to Lefty's back, Kai tried to shake him by blasting him off the bison. However, the bandit's security line prevented him from falling and the two engaged in a fight, during which Kai was lightly cut by the man's blade. As the supplies were lifted off Lefty, the young airbender jumped after them without hesitation, though plummeted toward the ground due to the damage inflicted to the right wing of his wingsuit. He was able to stabilize himself when Opal grabbed his arm and served as his wing, enabling them to land safely on Lefty.
After returning to the state capital and informing the governor of the loss of their supplies, a dejected Kai pulled out Kuvira's contract and told him it was time to make a tough call. Upon being handed the signed deal, the young man attempted to reassure the governor that he made the right decision, though was left with a heavy feeling upon being told that there never truly had been a choice. Kai flew toward the border and handed the signed paper over to Kuvira, who promptly returned with supplies.
Defending Republic City
Weeks later, when Kuvira marched her army down to Republic City, Kai oversaw her arrival from atop a roof, together with Jinora and her airbending family, and was shocked to see the approach of an enormous mecha suit. After President Raiko surrendered due to the overwhelming power of the spirit energy cannon that destroyed the United Forces' fleet in mere seconds, Kai retreated to Future Industries, where Korra elected him to be part of her stealth team of airbenders who would kidnap Baatar Jr. from his airship. He remained atop the vehicle with Jinora, while the three adults infiltrated the vessel. Together, they caught the bag containing a bound and gagged Baatar Jr. when the others airbent him out of the hatch and they all flew off to safety. He was forced to run for his life, however, when Kuvira traced Baatar Jr.'s radio call toward the factory and blew it up with her spirit energy cannon.
Kai managed to survive the explosion and emerged from the rubble with everyone else when Bolin lifted a large piece of concrete. While Asami and Varrick attempted to adapt the prototypes of the hummingbird mecha suits in Asami's office to get them airborne, he and the other benders faced Kuvira and her army in an attempt to stop them or at the very least, slow them down. On Meelo's urging, Kai and the other airbenders equipped themselves with balloons filled with paint. As they approached the suit, Kuvira fired at them; although the beam missed, the power it emanated was enough to throw them off course and Ryu slammed into Kai, causing them both to tumble down. Kai managed to save them both, however, by managing to make it to the ledge of a nearby building and hauling Ryu on it as well. They both recovered and resumed their mission. Upon reaching the enormous mecha suit, they dropped the balloons on the suit's windows, momentarily obscuring its vision and enabling the earthbenders on the ground to tie down the suit's legs. As Bolin gave the signal, Kai and the other airbenders blasted the suit with air currents in an attempt to topple it over. The suit managed to stabilize itself, however, forcing Kai and the others to flee when Kuvira aimed her spirit cannon at them. He checked up on Ikki, who was sitting dazed on the ground, before they all retreated to Asami's office.
Kai took part in the new plan to slow down Kuvira's progress that stated that the benders would relentlessly attack the mecha suit to distract Kuvira and enable the two hummingbird mecha suits to land on the enormous machine and cut a hole in it without being crushed. When Kuvira aimed her cannon at Korra, he joined Tenzin, Bumi, Jinora, Ikki, Meelo, Daw, and another female airbender to form a tornado in their wake and swoop down on the weaponized arm of the suit, knocking it out of balance and distorting its aim.
Defending the spirits
In the aftermath of Kuvira's defeat, Kai joined Jinora and several other airbenders in a meditation session at the new Republic City spirit portal. Their session was interrupted, however, by the appearance of Wonyong Keum and his construction workers, who threatened to call the police if they did not get off the land he had purchased to turn into an amusement park. Kai, refusing to leave the area surrounding the portal, which they now considered to be sacred land belonging to the spirits, supported Jinora as she told off the businessman. The heated discussion was interrupted by Korra and Asami's return from their vacation in the Spirit World, and Kai smiled in support when Opal assured the Avatar that the airbenders were on her side and ready to help protect the portal.
Later that night, Kai had to make good on that promise, as the portal came under attack by the Triple Threat Triad, hired by Wonyong to scare them off the land he had purchased to turn into an amusement park. The battle came to a quick end when Team Avatar arrived, as well as several angry spirits, who drove away the Triple Threats.
Kai, along with Tenzin, Jinora, Ikki, Meelo, and Ryu, joined Korra on her mission into the Spirit World, where she hoped to be able to reason with the spirits and convince them that the Avatar was and would always be the bridge between the spirit and physical worlds. Upon entering the Spirit World, however, they discovered that the once vibrant field of flowers that Republic City's spirit portal led to was now barren and seemingly burned down. Kai wondered who could be responsible for such a level of destruction and, as Jinora explained that only the spirits could have done that, did not understand why they would ravage their own environment. He was told by Korra that the spirits were using the destruction to send a message to the humans, which proved to be true moments later, as Kai found himself attacked by vines of the scorched spirit flowers, which ensnared his legs. He was saved by Jinora, who pulled him out of the vegetation's grasp, and the entire party rushed back through the portal. Before they could recover from their ordeal, however, they discovered that Raiko had ordered the United Forces to erect a perimeter around the portal, much to their dismay.
While living by himself as an orphan, Kai sported a cunning and opportunistic attitude and he would deceive and use those around him to benefit himself. However, when he allows himself to get to know the people around him, he shows a more emphatic and compassionate side, as evidenced by how he appreciated Jinora training him in airbending, as well as how he protected Yung against the Dai Li. He is protective of those whom he holds dear and is willing to be merciless to ensure their safety, such as saving Jinora several times, assaulting Ganbat for attempting to kidnap Jinora and the baby bison, as well as to risk his own life, as evidenced when he attempted to distract P'Li in order to give the other airbenders a chance to escape. Overall, Kai is a mischievous, yet fun-loving, young boy who takes every opportunity for adventure, and is willing to sacrifice himself in order to save those whom he holds dear.
Kai is a capable airbender, even though he is relatively untrained. He was able to use significant air blasts to knock Mako and Bolin onto the monorail, allowing him to escape, as well as directing specific gusts of air to facilitate his thefts. After training while held captive by the Dai Li, Kai displayed remarkably improved abilities in combative airbending, being able to knock out the Dai Li sergeant while rescuing Jinora in a single maneuver. During training with Tenzin, he was also the third one up the cliff and airbent to the top while the other recruits crawled. He completed the obstacle course relatively easily compared to the rest of the airbenders, showing his skill compared to the rest of the group. By the time the Red Lotus arrived, he could use a glider to fly and to attack at the same time. He is also capable of using a range of airbending techniques such as an air shield, which enabled him to survive a direct hit from P'Li's combustion blast. After three years of training, Kai improved significantly, being more proficient and precise in his airbending attack.
Kai is stealthy and evasive, as he was able to slip away from Team Avatar when they arrived in Ba Sing Se, with Bolin noting that he is "surprisingly hard to catch", as well as being able to follow P'Li's airship without being detected. He is also a good liar, as he managed to convince Team Avatar to believe his story before the sheriff arrived. He can make quick decisions, which also makes him a very skilled pickpocket. His thievery skills further extend to lock-picking, which he used to free himself from a cramped metal cage.
- Kai was designed to be an adventurous child with a slightly shadowy background, incorporating aspects of both Aang and Wan.
- Joshua Hamilton, who wrote the first episode in which Kai appears, named him after his son.