Aya Iseshima is walking home with her best friend Natsume Honma from their high school, when they walk right into the middle of a fight between a teenage girl dressed as a shrine maiden and a young woman dressed as a flight attendant. The priestess looks like she is in trouble, so Aya beats up Rei Kakizaki, the flight attendant. The priestess is thankful and introduces herself as Miko Kazuki. She has been fighting in a tournament in which the prize is a gem called the Martial Heart (Platonic Heart) which can grant a wish. Aya, Natsume, and Miko become friends, and since Miko's wish of making friends is now granted, she withdraws from the tournament. However, later that night, Aya discovers Miko's apartment has been ransacked with Miko nowhere to be found; she realizes that the Martial Heart not only grants the wish of the winner, but also banishes the losers.

Aya's new friend Miko disappears without of trace and it seems she never existed. Aya now has to compete so she wish her friend back but her next opponent is her favorite teacher, Azusa Suma.

Aya is in a sea of turmoil as she wonders whether it was really Haruki Honma, Natsume's brother, she saw as the leader of the martial heart and her semifinal match is in a maid cafe. Her opponent is Rin Hiroishi.

Aya faces her final opponent, Ryu Getsurei, a lady in red who says she is a clairvoyant who can see her heart.