Hitozuma ni Natta Onee-san ~Manatsu no Omoide~ + Save

The main character is Kota, a slightly shy male student.
One summer vacation, his parents go on a trip, and a distantly related woman, Yui, comes to take care of his incapacitated personal belongings.
When she was little, she was the first love person to spend her summer vacation with.
Perhaps because she got married a few years ago and became a married woman, the hero is attracted to Yui, who is gentler and sweeter than before, and hits an uncontrollable desire.
The relationship between the boy and the two, who should have been older sisters, gradually deepens.