Itsuki is a student 18 years of weak appearance, one day while walking down the street is surrounded by a band of criminals, Murashige Ryouta tries to save him but Itsuki is perfectly able to defend himself from the thugs because he practiced Aikidou. Ryouta is impressed with the strength of Itsuki and follows him to the house of his family. Ryouta begins to have a great fascination with the Aikido but even more by Itsuki