Daisuke is the shy main character who shares a body with the alter ego Dark Mousy.
Daisuke Niwa is on his 14th birthday when he decides to reveal his feelings to his young crush Risa Harada. He finds out that she finds him like a "good friend" before he manages to give her the envelope containing his confession. This realisation triggers a chemical reaction within his body transforming him into Dark Mousy. His mother, Emiko Niwa, reassures him that it is a hereditary condition passed down through the male descendants of the Niwa family. To return to normality Daisuke has to have his love returned to him.