Kai

Information
Kai (also referred to as the Fire Maker by the Ice Fishers) is currently the Elemental Master and Ninja of Fire, Nya's brother, and Ray and Maya's son. He and his younger sister worked as blacksmiths in their father's blacksmith shop all their life until they met Master Wu. With his guidance, Kai learned Spinjitzu and discovered his other teammates, Cole, Jay, Zane with whom he embarked on many adventures; battling the likes of the Serpentine and the Stone Army.

After Zane's sacrifice to destroy the Golden Master, the Ninja parted ways before reuniting to go rescue Zane on Chen's Island. There, Kai grew closer to Skylor, one of the tournament contenders, as they competed in the Tournament of Elements. Ultimately, he allied with the other Elemental Masters to defeat Chen's army. After the war ended, Lloyd was possessed by Morro, who escaped the Cursed Realm and released a legion of ghosts. Kai and the Ninja battled Morro and his forces before the Cursed Realm was destroyed. The Ninja found fame after saving Stiix, but when Nadakhan returned with the Sky Pirates, Kai was the first of the Ninja trapped in the Sword of Souls. Jay freed him and reversed recent events with his final wish. On the Day of the Departed, Kai and Nya fought a revived Chen, who they defeated once more. When the Time Twins returned to Ninjago, Krux tried to convince Kai that Kai's parents were traitors. Kai and Nya reunited with their parents and stopped Krux and Acronix from changing the future. They managed to track them through time and stopped them before Wu sent Kai and Nya back to the present, while Wu ended up lost in the time.

Early life
Kai was born in Ignacia, the first child of a blacksmith named Ray who owned the Four Weapons shop. He and his younger sister, Nya, were raised in their father's craft. Unknown to either of them, their parents were the Elemental Masters of Fire and Water. Kai inherited his father's element of Fire while Nya inherited their mother's ability of Water though they were unaware of this fact at first. When his parents disappeared, Kai took it upon himself to keep the family business going, vowing to surpass his father's blacksmith skills. Kai also took care of his sister while wondering all their life what became of their parents. At one point, the two had a babysitter named Grub Miller who they disliked and would trip when she made them go to bed early.