Monsters are individuals with the power to metamorphose into animals and are forced to live apart from the rest of society. Riku built a bond with Tsukasa, a Monster lad, in his early years, but they were forcefully parted. Riku has reunited with Tsukasa in a school for Monsters, but he needs to conquer biased attitudes from his fellow non-human monsters if he intends to revive their relationship. Will their grown-up companionship be as formidable as the one from their youth, or will it become more robust?