Yukinari is a high school student who was never accepted by the girls for being short, and ended up being "allergic" to women, when played, it was as if touched a nettle.
One day after returning from school, he slipped down the drain of the tub and reached "Siren", a place where there were only women. Worried about his "allergy", attempted to return to Earth ... Miharu, a mysterious girl he met Yukinari in "Siren", Kirie, Yukinari friend and companion, Koyomi, a girl who suffers an "allergy" like Yukinari but with the kids, Tomoka, who looks like a little girl, and the Kazuharu noisy brothers and Risa Fukuyama peers will Yukinari adventure in the strange land of "Siren".