Shounen no Natsuyasumi ~Ryouta~

Ryouta, who has come over to play at the house of his female cousin Yayoi who is 6 years older than him, just can't beat her at anything. When he took a peek at her smartphone from the side, he saw something inappropriate on the screen that was different from what he usually saw. The day after this incident, Yayoi calls Ryouta over to her room. "Yayoi has been acting weird ever since that day." Set in the same universe as.