Based of the erotic game by Candy Soft. 
 
The Hanabishi family and Hidaka family are next door neighbors. The fathers of both households could be called best friends, so they all get along like one big happy family. In particular, Hidaka family’s only son Kouki was raised lovingly by the four Hanabishi sisters like he was their own brother. One day, the Hanabishi and Hidaka parents were preparing for a long term overseas business trip together. Kantaro Hanabishi had only one problem holding him back from the trip; leaving his four daughters behind in Japan. 
 
“Leave it to me. You can rely on me to watch over them!” 
 
As a result of Kouki’s casual announcement, both parents happily departed on their trip. 
 
“Ooh, how reliable! That was what I was waiting to hear!” 
 
Between both of the parents, they had arranged for one of the four sisters to become Kouki's fiance. After Kouki's graduation they would continue discussion of it further, but this recent event gave a chance to accelerate their plan. Thus, all summer vacation Kouki will spend time alone under one roof with all four of the Hanabishi sisters. 
 
The eldest daughter Yurina: Despite being good at her job, While at home she lazes around and makes Kouki work hard. 
 
The second born daughter, Momone: Absolutely adores Kouki, and does nothing but spoil him. 
 
The third daughter, Saori: She does all the housework, and although she is like a maid she prefers it to going outside. 
 
The youngest daughter, Anzu: Has no reservation in calling Kouki her personal play toy. 
 
Each of them have their own motives doing anything they can; at times even tempting him into sexual situations, so they can draw closer to making the Kouki they love their husband. If Kouki ever chooses a bride, who will it be? The energetic life with the quartet of sisters is about to begin.