Adult PC Game: Ane Mas -The Ane Master- by Cowper Archive

Makoto is just an average student. He has a beautiful older sister, Kotone. One day, their parents go abroad on business, so there are only Makoto and Kotone at their home. They are confused because they love each other.... But their aunt, Ayaka, comes to their house to take care of them. They are somewhat relieved.... Months later, Jun, their friend, comes back to their town. Since the day Jun comes back, Makoto and Kotone's life gradually changes. Involving other classmates, Makoto is surrounded by beautiful girls....