Niwa Daisuke's life was never that of a normal teenager. Growing up with his mom and grandpa, he has been trained in the arts of theft, and he has become a master at it. On his 14th bithday, a wierd change occurred... and in a startling transformation, Daisuke become Dark Mousy, the phantom thief! However, Daisuke can only transform into Dark when he see's Risa, his crush. Likewise, Dark can only transform back into Daisuke when he sees Risa's twin sister, Riku!
With every passing theft, Dark grows stronger, and so do his opponents. Just as every hero has an enemy, so does Dark. Satoshi Hiwatari, a child prodigy and the commander-in-chief of the police squad set to capture Dark. Just as when Daisuke became Dark, so did Satoshi become Krad, the white-winged counterpart to Dark. Unlike Dark, Krad doesn't seem to care about other lives, despite his seemingly "good" colors. In the past, though, it was Krad who sealed both him and Dark into entrapment. With the final battle between Krag and Dark drawing ever nearer, will Daisuke and Dark be able to overcome evil? And will they both finally be able to declare their love for Risa and Riku respectively?