Kurenai is a legendary mercenary who paints the battlefield crimson. Having completed missions on numerous battlefields, he has been given a new mission: to teach at a Japanese high school. He travels to Japan under the name of Echizen Shota and learns the details of his mission: to protect a female student named Kujo Sakurako who attends the school. Having grown up on a battlefield and never having had anything to do with a woman, will he be able to complete this most difficult mission of all?