Taro Sado is the hero of the story, and a true masochist.

He went to the same middle school as Yūno, who is at fault for turning him into a masochist. He is not sexually attracted to his relatives, though his mother and older sister are attracted to him and have an over protective relationship for him. 

He is sometimes forced to perform cross-dressing (in the anime he was cross dressing because he was hypnotized to by defult, love Tatsukichi who which tries to avoid Taro by cross dressing). Taro is known to have a ridiculous amount of "Pervert Energy" (over 30,000 units, while 5 units for average people.), which was employed by Noa in one of her schemes. 

Despite the fact that he is a self-proclaimed "Super Masochist", Taro won't hesitate to help out his friends such as rushing Mio to a hospital when she collapsed during their mock-wedding at their date, trying to beat up the senior who attempted to sexually assault Arashiko way back despite being outmatched, acknowledging Tatsukichi's cross-dressing and telling him that he doesn't mind. 

His surname Sado is probably a pun on sadomasochism which is particularly displayed in a wide array of scenarios throughout the series.