Natsuru Senō wakes up to discover one morning that he has transformed into a woman, upon which a stuffed animal tiger, Disemboweled Tiger, who introduces itself as a messenger, tells him that he has become a Kämpfer, which must do battle with other Kämpfer; since Kämpfer must be female, Natsuru transforms into a female version of himself.

Natsuru stops Akane from shooting Kaede and the attacker escapes when the bell for class rings. Natsuru realizes that the enemy also goes to his school and becomes wary of the danger and cautious of the other girls around him.

Natsuru begins his first day in the girls side of the school where he is transferred into Akane's class and is very popular among the girls. Kaede confesses her love to Natsuru, but he is unable to answer due to his bracelet flashing.

As the cultural festival comes up, Natsuru is shocked to find that Shizuku has entered him into the Miss Seitetsu beauty contest.

The cultural festival is about to begin and the class dress Natsuru and Akane in various costumes for the Miss Seitetsu beauty contest. In the changing room, Kaede interrupts the two of them and once again gets into an argument with Akane.

Natsuru is surprised to find his childhood friend Mikoto has returned. When Kämpfer Natsuru heads to school, she is forced to participate in a 'quasi-maid café'. She is later accompanied by Shizuku, who warns her that a new Kämpfer will be coming.

Natsuru, unexpectedly accompanied by Akane and Shizuku, arrives at Kaede's house, which has a lot of Entrails Animals. Kaede starts things off with a game involving two people biting through the ends of a Pocky stick.

Akane is having a romantic summer date with male Natsuru at the pool. However, Mikoto, Shizuku and Kaede show up as well.

Natsuru finds himself sitting next to Kaede outside the hotel, who hypnotizes him into making Shizuku his.

Shizuku invites Natsuru over to her house to tell her about Kaede, getting Kaede's Burnt To Death Lion to spill the beans about the Kämpfer system.

Natsuru wakes up on Christmas Eve morning to find out that he and his messenger, Disemboweled Tiger, have swapped bodies!