[Before writing about the Niwa family's history, please make sure to check our spoilers policy! Don't spoil what hasn't been scanlated and released on a publicly accessible site/officially translated.]
Main Article: Daisuke NiwaTypical 14-year-old schoolboy with a crush on Risa Harada. On his 14th birthday, his "love gene" activates, causing him to turn into Dark Mousy whenever he feels love; even a picture can trigger the gene. Daisuke is very kind-hearted, and often tries to stop Dark from doing crazy stunts, such as stealing art and flirting with girls.
Main Article: Emiko NiwaEmiko is Daisuke Niwa's mother. She makes unusual clothes for Dark when he goes out to steal artwork and is also responsible for sending out the notices to the police that tell them what, when, and where Dark's next target will be. Emiko is very much in love with her husband, Daisuke's father Kosuke Niwa. She has a very peppy personality, and views Daisuke’s transformation as cute.
Kosuke Niwa Edit
Main Article: Kosuke NiwaKosuke Niwa is Emiko Niwa's husband. He is shy and thoughtful. He married into the family and adopted the surname. He knows a lot about magic and journeyed far to research, not seeing his son for many years until he finally returned when Daisuke is 14. He sometimes provides rings or bracelets with magical properties to help people.
Main Article: Daiki NiwaDaiki Niwa is Daisuke's grandfather and Emiko's father. Daiki was the original Dark 40 years before the series takes place. He took the task of stealing during his time as Dark as though it was his job. With the aid of his daughter, Emiko, he prepares Daisuke for his destiny. During the anime, he randomly wanders around town gaining information about Dark's potential targets.
Main Article: Daichi NiwaDaichi Niwa is an anime-only character: Daisuke's future child, presumably the child of the couple Riku and Daisuke. He is only seen in episode 13, when Towa brings Daisuke twenty years into the future in order to retrieve the stone that will allow Dark, Saehara and Risa's souls to return to their respective bodies. Daichi stole the stone from the fountain and brought it back to Emiko and Kosuke's home. Though it is possible that Daichi is not Riku's child, he shares some of her features.
- Every known male descendant of the family has a name that begins with the letter D. That means all of them have the initials "DN".
- Daisuke Niwa is the first member of the family to create a piece of art.