Jun Yamamoto

Jun is ranked 3rd in school and is Megumi's younger twin brother. The son of a music producer and a talented singer, Jun loves music more than anything else, but ironically has little talent for music. Usually quiet and kindhearted, Jun has a split personality which he has concealed from everyone except Megumi and Ryuu. Triggered whenever he is kissed by a girl or receives a lot of affection, he becomes irrestible to nearly all women and is able to charm them effortlessly. His split personality resulted from an hypnotism program that Jun watched as a child and first emerged when he was still in grade six. During a date with a girl, he changed and all the other girls around him became mesmerized by him; this led the girl Jun was dating to hate him and call him disgusting. The only thing that can bring him back to his original self is by losing consciousness.

Source: Wikipedia