In Japan, "Samurai" maintain order by using their supernatural powers to slay mythical beasts that bring disaster to humanity. Shinnosuke, an ordinary salaryman, one day witnesses a "mythical beast disaster" right before his eyes, but to save his sister Himari, he unleashes his hidden, unparalleled swordsmanship and slays the beast! Surrounded by beautiful girls such as his childhood friend Satsuki, who has already become a "Samurai," and Shizuna, Himari's classmate and the daughter of his boss, he carries out his duties and missions!