One morning, the protagonist, Misono Masuta, sits down at the breakfast table as usual, but something feels off. The other four members of the family — his wife, son, daughter, and elderly father — are talking about sexual matters as casually as if they were discussing the weather.

Then, when his wife notices the son being troubled by a morning erection, she simply says, "what do I do with you", and, treating it as the most mundane of acts, begins to perform fellatio on him right there at the table.

Masuta is stunned and thrown into chaos, but the rest of the family merely glance over and ask if he’s okay. Even while reeling, he finds himself massively aroused by the situation and ends up having sex with his daughter.

That's when it hits him: he has somehow arrived in a world where anyone will sleep with anyone, no questions asked.

Masuta decides to make the most of it. In this bizarre yet casual atmosphere, he uses the perverted inventions his unhinged old father created to relentlessly have his way with his wife and daughter, does the same with his son, even brings the family dog into the mix, and impregnates his family. With threesomes and foursomes available on demand, the days of escalating debauchery blur together...

[Translated from Getchu]