|Japanese name:||瀬能 ナツル|
He is involuntarily chosen to be a Blue Kämpfer by the mysterious Moderators and is set up as a Zauber-type Kämpfer with powers based on conjuring fireballs. In keeping with the rule that all Kämpfer are females, he turns into a girl upon transformation. In Kämpfer form, Natsuru's male student uniform automatically changes into the uniform for female students, including his underwear and vice versa when transforming back to normal, while his short blue hair becomes slightly longer, which is always arranged in a style that ties it up like a ponytail.
After a fight with Shizuku exposed his Kämpfer form to other students of the school, Shizuku arranged to have his female form enrolled in the girls' side of the school to fulfill public curiosity in a way that diverts attentions away from Kämpfer battle.
His Kämpfer form has subsequently been ranked among the Three Beauties of Seitetsu (there used to be only two, being Shizuku and Kaede). Much to his own dismay, his female form becomes the subject of intense affection from Kaede Sakura (who has displayed no particular interest in his normal male form), nearly the entire the female student body, and the boys, including his male classmates. As a Kämpfer, the messenger assigned to Natsuru by the Moderators is Disemboweled Tiger, a plush toy that is part of the Entrails Animals series of stuffed toys.
Voiced by: Marina Inoue