It is revealed that Yujin is a robot working for Leviathan.
Yuujin is a teenage boy with fair skin, spiky red hair, and green eyes. He wears a green shirt with yellow on the chest, white on the sleeves and three black lines on the shoulders, greenish grey shorts, dark green socks, and white and green sneakers wit dark green soles. It is later revealed that he showed them his robotic arm.
Later on, he wears a dark suit and a red cape. On his chest, he has the Leviathan symbol.
Yuujin is a good friend of Haru the Applidrivers. Until he sent Shutmon to kill Bootmon and get his chip, it's revealed that Yuujin is actually a robot that works for Leviathan.
Haru, refusing to fight his own friend, tries to Yukon from obeying Leviathan's bidding. After Leviathan's body was destroyed, Yuujin felt remorseful for his actions and apologizes to the Applidrivers, and decides to delete Leviathan's permanently, thus costing him his life. In the final episode’s climax, Yujin was brought back to life.