Seraph of the End, Vol. 4 — Takaya Kagami

A vampire attack reunites childhood friends Yuichiro and Mika, though they now face each other from opposing sides of the battlefield. Mika begs Yuichiro to forget about the conflict between humans and vampires and escape with him, but Yuichiro is unable to abandon his new friends. Then, everything changes when Yuichiro suddenly transforms into a monstrous being with one seraphic wing!