White x Red

Main character belongs to an exorcist lineage. Incidents start to become more frequent in his home town, so he interrupts training and returns to help the town. His father insists that son must marry to become a full-fledged exorcist, so protagonist starts living with his possible bride candidates including childhood friend and sister. Sex serves as source of spirit power required for exorcism, so young people are officially allowed to to involve in different kinds of sex play.

[Modified from vndbreview]