|“Kai, Master of Fire. His desire to protect friends and family burns as hot as his temper.”|
|— Zane describing Kai|
He is the eldest son of Ray and Maya, as well as the brother of Nya and another. Kai was the fourth ninja to be chosen by Wu, alongside the three other ninja. Soon, Lloyd and Nya joined alongside the Ninja. Years later, the Ninja went to Camelot and had to go through series of tests by Sir Lancelot, and without question, Kai did them all, and he did them correctly, while the other Ninja failed. This caused the Ninja to go back in time to the Revolutionary War, and the only way to stop it was to find baby Lancelot. When their leader Colten supposedly died in battle, the Ninja split up and went their own ways until Colten came back to them.
When the Overlord gave up on defeating King Arthur and his army, he went back to the Realm of Death. Kai and the others went back to Earth but landed on Chen's Island, where they were caught and imprisoned for a month.
When he was possessed by Rex Dangervest to work alongside him, his friends helped him work a way out of it, and also fighting Zane to make him good again. When he, Cole, Kai, Wu, Wu's son, Charles, Charles Wallace, Zane, and Jay was trapped in Jumanji under the Oni's control, Lloyd and his friends tried their way out of the jungle, even after finding those Oni helped them and the Omega lied to them about the real Oni. They were really Spinjago citizens in disguise, and they helped Lloyd and the others go back to Earth.
- Main article: Kai (Relationships)
- Kai shares his name with a frog from Sing.
- Kai and Skylor are one of the Ninja-romances to become a couple, the others being Zane and Pixal, and Jay and Nya.
- Main article: Kai/Gallery