Shuntaro, the protagonist of this story, was not much different from a typical Japanese nerd who does not have a girlfriend and spends all his free time in eroge simulators. The only thing that set him apart from the crowd of dull hikikomori was the presence of three younger sisters. The girls hated with all their hearts their pervert brother using their panties instead of napkins while masturbating. Shuntaro, after the next lulls from the loving sisters, made his dreams of an older sister come true with the help of computer games. One day, his fantasies came true. But not in the usual hentai plan, when a sexy beast literally falls on the hero's head from the monitor screen. He just woke up in the morning, being 10 years younger than himself, becoming the proud owner of as many as THREE older sisters. Pretending to be a friend of Shuntaro (himself), he began to embody his sexual fantasies.