Itoshi no Betty Mamonogatari

When Tanpei Kimokawa comes across a nearly naked girl injured in a railyard, he drops everything to administer first aid. Only afterward does he realize that she bears a stark resemblance to the girl tattooed on his back. Some time later, when he finds himself overwhelmed by thugs, that same girl returns to protect him.

He soon learns that the mysterious girl is Betty Valentine, a witch from the demon realm who has traveled to Earth in order to get revenge on the demon that killed her sister. Not caring about her origins, Tanpei accepts her, and they quickly fall in love. However, if Tanpei is to appease Betty's family, he will have to prove that their love is strong enough to overcome a series of trials.