The hero of the story, though he doesn't seem like it much. Yu-Da was raised by his kind grandpa who was killed by Foxes when he was in the fifth grade. He was outcasted a little bit by his peers because of his background of having no parents and living in a poor part of the city. Even Myung-Ee made his life difficult by getting angry at him. His fifth grade personality was somewhat serious. He's known to be kind, not snobby, but he teased Myung-Ee on her hair and her rabbit print underwear.
Five years later, he's the Secretary of Chun-Ah High School's student council. His personality is completely opposite of what he was five years ago. He smiles a lot, wears glasses, has an unusual talisman on his hair, and is extremely kind. Can be considered the peace maker among the student council. He's currently living with Se-Eun because he's the "black rabbit". His liver has special powers that can grant the Fox, who devours the liver, an immortal life. So, he has to be protected by the student council, which consist of all Foxes. In order for the Foxes to watch Yu-Da, his memory had to be altered so he doesn't remember anything from five years ago.
When Yu-Da's glasses come off by either some kind of force or any other way, he becomes a completely different person known as "Black" Yu-Da. He wears his school uniform unbuttoned and loose. His expression is very cold, calculating, and very confident. Also, his "black rabbit" power is super strong at this point. He can hit Foxes without touching them. He doesn't even need a Ho-Se sword. Another ability he can do is erase/alter people's memories.