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 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.