As punishment for a certain incident, Mark, a high ranking demon, is ordered to work on Earth.

Then, a pure and baby-like new angel, Ten, is sent to him! Though Mark is bewildered by his superior's order that being this angel's "instructor" is part of his job, he finds himself unexpectedly enjoying their days together- Salivating over Ten's blessed, beautiful body, taking care of him, and teasing him a little...

Then, one night, Ten ends up giving Mark a private lesson in "purifying sin" using his body...?!