Based on the manga by Yoshiron. A man’s wife left him for another man, leaving him and her own daughter, Nanakura Kasumi, behind. Frustrated, one night he comes to his stepdaughter… (Source: AniDB)

The four daughters of the Onami household—Sora, Akane, Kohaku, and Sumi—have set some “rules” for their brother to follow when hugging them. He must make sure that each hug is: at least 10 seconds long; accompanied with a sniff; and, most importantly, done with lots of affection. Of course, these stipulations apply not only to mere hugging, but also to even more intimate acts. [Written by MAL Rewrite]

Based on the adult manga by Yokoyari Mengo.

The hero’s family hires a “sugar sister” named Hinano-san to take care of him after school. The two fall for each other and have several sexual meetings.