My Sadistic Boyfriend Volume 4

Chiaki and the unofficial school prince Katsuho are roommates - as well as boyfriend and girlfriend. On the surface, Katsuho is by all appearances a dazzling prince. However, when alone with Chiaki, the prince becomes a sadist with a perverted streak!
The school is in an uproar over the sudden news that Mitsuru, a handsome boy second only in popularity to Katsuho, will be leaving to study abroad. Worse still, it appears that Chiaki's best friend Mamiya may be leaving with him. As Chiaki contends with the loss of her friend, she begins to notice that Katsuho is acting unusual...