Series by 桜井亜都

Mikado Chiaki is a high school boy who lost the ability to feel joy after a strange three-headed dog bit away a piece of his soul as a child. Years later, a mysterious package arrives from his father, containing a girl named Kuro who claims to be Cerberus, the mythical guardian of the underworld, with three distinct personalities sharing one body. Kuro declares herself Chiaki’s protector, aiming to help him reclaim his happiness, while her other forms—Shirogane and Roze—bring their own quirks and affections into his life.

Ever since a childhood accident where Maruna Rinjou saved his life with a blood transfusion, Haruka Kuze has felt a deep sense of gratitude and a desire to repay her. But Maruna, now a fiery and determined girl, seems to want nothing to do with him—or so he thinks. When Haruka discovers that Maruna is a "witch's egg," struggling to wield magic on her own, he decides to help her achieve her dream of attending the prestigious Sacred Witch Academy. There's just one problem: it's an all-girls school, and Haruka must go to great lengths to support her.