Noboru Kusakabe is an 18-year-old virgin who has a mortal fear of big breasts thanks to a childhood trauma. When his friend Takahashi convinces him to go to a mysterious brothel called Devil Ecstasy, he meets a beautiful girl with tiny breasts named Meruru and falls in love - but all is not as it seems. Devil Ecstasy is a front for an army of succubi who want to take over the world, and Noboru somehow has to stop them