Ten De Shouwaru Cupid summary:

The Koinobori yakuza family's souls are expensive commodoties, a source of great pride to those of the demon world's soul bank. But when the Koinobori heir, Ryuji, is born with a pure soul engrossed with fairies and angels, it's up to Maria to become his personal cupid and reform him so that he continues the Koinobori's lascivious family line!