The main character, Takafumi, has secret feelings for his older sister who is both intelligent and beautiful. Since his parents are working overseas, he lives with his older sister and gets along well with her.

One day, Takafumi witnesses his older sister Mayumi having fun with another man on her way home from school. Seeing her smile, which he had never seen before, Takafumi is attacked by intense jealousy. If this continues, his sister will belong to another man.

At that time, Takafumi consults an incestuous relationship community site that he found on the internet. So he decides to follow the advice he received and order the tools to make his sister his own. He must take action before her sister becomes another man's property. Takafumi's plan to reclaim his dear sister has begun.