"Boy, why do my sisters all have to have great bodies and big breasts? I don't know whether to call this heaven or hell; I mean, they are my sisters. I want to touch them, squeeze them, suck on them... Hmmm, maybe I should at least give it a try. After all, we aren't related by blood..."
Keisuke lives in with 10 sisters, they all have great bodies and boobs, but he can't touch them because they're relatives... or can he, follow him on his quest to have sex with all of his sisters.