"With my legs, I'll do anything you want…?" Torasuke suddenly meets a girl with the perfect legs, but her true form is… a mermaid?! With zero experience in love, Torasuke is obsessed with legs. One day, he matches with Karen, who has his ideal muscular legs. They even hit it off right away! However, when they meet, he discovers her lower half is a fin! When nervous or excited, she transforms back into her mermaid form. To maintain her human appearance, Karen needs to get used to being around guys. Dreaming of those amazing legs, Torasuke and Karen begin to live together?!