絶対★妹原理主義!!

As the heir of the family dojo and their only brother, Takuma wants to set a good example for his four imoutos and trains hard every day. However, the oldest imouto Mizuki suggested one day that they tear down the dojo and build a shop instead. All the other girls quickly agree and so it becomes a battle between him and his imoutos for the fate of the family dojo! In order to win him over, they plan to seduce him all the time. Will he be able to fight off their advances (and his own primal urges) and preserve the family dojo?