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]