Onee-chan no Ama Ero Lesson ~Sewayaki Kyonyuu Onee-chan-sensei ni Tappuri Amaeru Mecha Ero School Life~

The protagonist, Yuuya Asahina, lost his parents when he was a child and was taken in by his grandparents far away. He also had to say goodbye to his childhood friends, who were like older sisters to him. What gave him strength was a promise: "When I grow up, I