In the old days, there was still a shogunate in Kamakura. There was a powerful man who tried to borrow the power of the sea sword with the promise that he could eat as many humans as he wanted every fifty years, in order to keep his power lasting-time is now. Natsumi-chan, an outsider, is working together with the outsider children's darkness and Kidomaru to protect Kamakura from the swords and fight together today!

Alternative blurb

Natsumi, a self-paced high school girl, finds a long-haired beautiful young man lying on the beach at the 50th anniversary festival of Gaho Doji, and takes care of him. The young man's name is Kuroyami, and he becomes attached to Natsumi, but with the appearance of the Kagekoji family, the evil spirits of her spirit world, Natsumi's daily life undergoes a major change...