Species: Devil/Demon
Sex: Undetermined (but very masculine)
Age: Undetermined
Role: Satan's nephew, bugging Kohaku, satisfying his "appetites"
Descriptions: Mischievous, naughty, sarcastic, hot-tempered
Significant other: None, really, but he does have Ruri and Hari

Kokuyo

Species: Devil/Demon
Sex: Undetermined (but very masculine)
Age: Undetermined
Role: Satan's son, bugging Shuichiro, punishing Koryuu
Descriptions: Pragmatic, sarcastic, naughty, devoted
Significant other: Hisui, of course.

Ruri and Hari

Species: Devil/Demon
Sex: Undetermined (but probably girls, if anything)
Ages: Undetermined
Roles: Spying on Kohaku and Shuichiro, hanging over and around Koryuu
Descriptions: Fun-loving, amusing, mischievous
Significant other: Koryuu