My Sadistic Boyfriend(2008)

S Kareshi Joujou

Chiaki has been admitted to the high school of her dreams: the prestigious boarding school Otomegawa Academy. Through an unexpected turn of events, she ends up becoming roommates with Katsuho — grandson of the academy's director, and prince of the school. On the surface Katsuho is attractive, academically brilliant, and kind, appearing to live up to his prince-like reputation.

But when he's alone with Chiaki, his true, sadistic personality shines through. How will Chiaki juggle her new school life while fending off the advances of this sadistic prince?

(Source: Manga Plaza)