蛇神くんは寒いと変身しちゃうから

Synopsis

The transfer student, Hebigami-kun, has a peculiar trait: when he gets cold, he turns into a snake. Mysterious and feared by everyone, only his seatmate Haruna knows that he's actually kind-hearted. Unless his body temperature rises, Hebigami-kun can’t return to his human form. Haruna starts to worry about him and tries to keep him warm. (Source: Pixiv Comic, translated)