Dear My Mother

Shun and his (step-) mom, Hitomi, do it in different places and in different ways. Story? Not much. Shun teases Hitomi, then they have fun sex, a lot. They're supposed to be the same two from Scarlet Desire. At the end there's an unrelated chapter between an art teacher and her student.

(Source: MU)

Included one-shot:
Volume 1: Yuuwaku Erena-sensei