Niwa Daisuke

Daisuke is  a typical middle school student.  The only thing really unusual about him is his special DNA, which causes him to transform into Dark when he experiences feelings of love. He has a crush on Harada Risa.

Dark Mousy (Daaku Maujii)
Dark is the bishounen entity Daisuke (and his grandfather before him) becomes when he goes through his DNA transformation. He is described as "monku nashi de kakkoii," which means "perfect and cool," or just plain flawlessly attractive. Unlike Daisuke, he likes Riku better. In fact, his feelings for Riku cause him to change back into Daisuke.  Dark is a great thief, appearing for the first time in forty years.

With (Wizu)
With is the Niwa family's pet, but he's also the demon that serves Dark. He normally looks somewhat like a cross between a dog and a bunny, but he also changes form when Daisuke does, becoming a black-winged creature that also doubles as the wings on Dark's back.

Harada Risa
Risa is the younger of a pair of identical twins in Daisuke's class. She wears her hair long (a bit longer than shoulder length). Perhaps it's because she's the younger twin, but she has a sort of rivalry with her older sister, and she strives to beat Riku at something. Risa claims to be the cuter of the two, and she's working on getting a boyfriend before her sister does.

Harada Riku
Riku is the older of the twins. She's identifiable by her short, stylishly-cut hair. She's a bit more cool and composed than her younger sister. Lately, she seems to have developed a fondness for Daisuke.

Hiwatari Satoshi
Satoshi is cool, intelligent, and perhaps a little mysterious. Though still in middle school, he is a commanding official in investigating Dark. Personally, I don't think he's a bad guy; Satoshi gave Daisuke tissue when he was crying!