The 14-year-old protagonist of the story is a typical school boy who has a crush on a girl at his school, Risa Harada. However, because of the Niwa family heritage, his special DNA merged with that of the famed phantom thief, Dark, when he was rejected by Risa.
Daisuke can transform into Dark (usually unwillingly) whenever he experiences feelings of love or intimacy. Daisuke is kind-hearted, the opposite of Dark and always trying to stop Dark from performing crazy stunts to no avail. Later in the series, Daisuke gradually falls in love with his old crush's older twin sister, Riku Harada. Even though he does not look or act it, Daisuke is very perceptive and athletic - capable of jumping from heights that a normal boy could never be capable of. To hone his skills, his family sets up daily life-threatening trials once he returns home from school. A specialty of this is his gift for lockpicking (or hacking, in the case of electronically activated locks) any kind of lock in succession.
Daisuke, as a Niwa, has been trained in thievery all his life. He can dodge traps, pick locks, sneak past security, and break into almost any location. However, he prefers to create art, not steal it.