Ninja is the main character in I-Ninja.
Ninja has a reputation for being rash, short tempered, and even cocky. Ninja is a white belt at the beginning of the game, but throughout gameplay, his belts, strength, and weaponry increase. At the beginning of the game, Ninja is first fighting for his life against a group of Ranx on the selection screen.
Then, he encounters a few more Ranx guarding his chain-bound Sensai, whom he is trying to rescue from the evil conqueror, O-dor. He kills the Ranx with ease, displaying his mastery of his small katana blade. After cutting the chains bonding his sensai to the wall, a large dragon pops out of the earth. Ninja kills it by stabbing it in the neck, and a large red rage stone hovers over the creatures mouth. Despite his Sensai's frantic cries of "NINJA, STAY BACK!" An encaptivated Ninja grasps the rage stone, and goes into a fit of berserk rage, and flies into Sensai, knocking him into a flat, sharp rock, decapitating him. Shortly after regretting what he did, Sensai reappears as a translucent apparition or a ghost.
He tells Ninja that his grasp of Sensei being dead astounds him, while implying to Ninja, that it was stupid to not listen to him.
He then goes on to explain that there are more Rage stones, and that they would be crucial to Ninja's quest of defeating O-Dor. Ninja does, in fact, find a romance in the game. Zarola, whom he rescues on Mountain Gorge, a stage in the game. He sees her as a potential date while she sees him as a mild flirt.