Jinora and Kai first met in small Earth Kingdom village when Jinora and a group were searching for new airbenders. Kai happened to be one of these airbenders and said that he wanted to join. It turned out that Kai was a thief, but Tenzin decided to take him anyway because he would have been imprisoned. Jinora did not care about his past and soon developed a crush on him. She was seen blushing at him after she helped him and her Uncle Bumi practice their airbending.
Kai was eventually captured by the Dai Li so Jinora in the others went to look for him and the other airbenders. Korra suggested that Jinora try to find his energy because they have a special connection. It worked and Jinora was able to locate Kai. When she saw him, she immediately ran up to him and kissed him on the face. This caused Kai to blush. Bolin was excited and said that her father Tenzin would not be happy with this. The two later went to the Northern Air Temple with the rest of the airbenders.
After arriving at the Northern Air Temple, Jinora and Kai began to spend more time together. They flew off together to go watch the bison calves together. Kai ended up telling Jinora that she is an amazing airbender and asked why she did not have her mastery tattoos. Jinora was unsure that she deserved them but Kai encouraged her and she talked to her father about it. Later, the two went to see the sky bison again but were captured by poachers. Kai managed to get out of the cage and help her escape. They were later rescued by the other airbenders.
The Red Lotus later attacked the air temple in an attempt to hold the airbenders hostage. While the group was trying to escape, P'Li was firing at the airbenders with her combustionbending. Kai decided to distract her so that the others could escape and was seeming blasted out of the air. Jinora screamed Kai's name in tears because she thought that he was dead. However, Kai survived, but the airbenders were captured. Kai later helped Team Avatar find the airbenders. He and Jinora hugged when they were reunited and the latter was relieved to see Kai alive.
Kai and Jinora tried to come up with a way to help Korra who was fighting Zaheer in the air. Kai wanted to fly up to them on Lefty but they were too slow. Jinora instead led the airbenders to create a giant tornado to capture Zaheer, in which Kai joined. Three weeks later, Jinora received her airbending tattoos. Kai attended her ceremony. At some point over the next three years, the two began dating. Even though their relationship was long-distance at times, the two were still doing well as a couple.
The Kainora pairing became popular as Book Three: Change was airing. At first, there were leaks and Kai was revealed to be an airbender. Many fans assumed that he was Bumi's son until Jinora was seen blushing at him. The two would have been cousins if this was the case. This ship set sail as soon as it became canon. Some thought that the two were too young to be in a relationship but this was changed after the time skip for Book Four: Balance.
- This pairing was referred to as "Jinkai" on a nick.com poll.