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.
"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..."