D.N.Angel follows the adventures of Daisuke Niwa, an average teenage boy. At the story's opening, Daisuke declares love for his crush, a girl named Risa Harada, on his fourteenth birthday. She rejects him, and later that day, the heart-broken Daisuke undergoes a strange mutation that changes him into another person. He is told calmly by his mother Emiko that, because of a strange genetic condition, all the males in Daisuke's family gain the countenance of Dark Mousy, a famous phantom thief. The transformation occurs every time Daisuke has romantic feelings for his crush or whenever he thinks too long about her. Dark changes back into Daisuke the same way. Daisuke is forced to keep his family's secret and control his alter ego, Dark (who Risa, Daisuke's crush, has fallen for), while dashing his way out of being caught by the commander of the police. Daisuke learns that in order to return to normality, he must have his unrequited love returned.