Niwa (丹羽 Niwa) is the only known name of Daisuke Niwa's ancestor and the original tamer of Dark.
Niwa is nearly identical to Daisuke Niwa, with spiky red hair and red eyes. His clothes are all black, including black gloves and a black cape.
Niwa is confident and ambitious. His desire to steal all of Hikari's artworks leads him to form a rivalry with the artist.
He cannot feel happiness unless he possesses Hikari's artworks, no matter who suffers in the process.
Before Hikari became a famous artist, Niwa was already a phantom thief. The living artworks that Hikari produced obsess him and become his targets. They continue this cycle of creation and theft over the course of an unknown number of years.
When Hikari had nearly finished his masterpiece, Black Wings, Niwa arrives to steal it. As the thief reaches for the artwork, the magic ritual is interrupted, thus redirecting the magic onto the two humans present in the form of a divided curse. Niwa is cursed with Dark Mousy at this time.
He wakes up sometime later, reaching towards Hikari or the Black Wings and growing wings out of his back.