The main protagonist, a boy whose face inspires terror and despair in other people's hearts, but whose true nature is that of a kind-hearted boy. His gentle and caring actions mostly frighten those around him, and he's used to getting hit for no apparent reason at all, so he developed speed and reflexes which allow him to absorb the power of the blows; although he has no martial arts skill and doesn't like violence, this in itself is enough to make any skilled fighter lose their will to fight, so he's technically unbeaten. 

(Source: Wikipedia)

Seiichirou Kitano is a naive and kind boy with the heart of an angel and the face of a devil. Upon entering his new school he is presumed to be a villainous heroin addict, and unwittingly becomes the leader of the schools thugs, all thanks to his frightening face. 
His new "friends" have great expectations of him, seeing him as a frightful demon. Kitano himself on the other hand, loathes violence and is blissfully unaware of the situation he is in... Note: Includes 5 extra chapters

Angel Densetsu is a story about Seiichirou Kitano, a kind and naive boy with the heart of an angel, but the sinister looks of a devil. This causes many misunderstandings, leading people to assume that he is a villain or heroin addict, and results in a career as the head thug, or "school guardian" at his new school.
 
(Source: Anime News Network)