Hiroto lives with his four cute imoutos. One day, his father called him back home and unexpectedly introduced him to his new twin step-sisters. One of them is a famous idol, and the other is a popular cosplayer. He enjoys a happy life surrounded by six pretty imoutos fighting for his attention.

However, one day he injured his right hand protecting his stepsisters from stalkers. While he was praised by some for his courage in protecting his imoutos, there were others that were outraged at the fact that he lived with six imoutos. To temporarily escape the public eye, they decided to take a vacation in the southern islands.