Hibana - Asumiko Nakamura

From the mastermind behind Classmates: Dou kyu sei comes a dark romance about a girl, her boyfriend, and the transfer student he refuses to leave alone. Tomori knows her boyfriend Inukai has a cruel side - but when he sets his sights on Misato, the new transfer student, things take a disturbing turn. Inukai’s fixation spirals into torment, and no matter how hard Tomori and her friends try to stop him, the violence only escalates. But what begins as bullying soon blurs into something stranger, darker… and far more intimate.