High school student Yukinari has always been teased by girls due to his being vertically-challenged, so much so that he developes female-phobia (whenever he touches a female, rashes will break out).

One day, after returning home from school, he falls in the bathtub and is transported to Siren, a place inhabited only by women. There, he meets the mysterious girl Miharu, Kirie, a childhood friend, classmate Koyomi, who suffers male-phobia, Tomoka, who looks like a child, and the noisy siblings Fukuyama Kazuharu and Risa. They all create a host of problems for Yukinari.