looking for a doujin about a boy that has a crush on a sempai, so he practices confessing to her with he sister of the crush, he later finds out that the sempai has a boyfriend and when he faces the sister she laughs it and has sex with him. in the end they become a couple after he confesses to her. it was on this site many years ago but i cannot find it anymore. any help will be appreciated. the doujin was like 3 chapters long and i was all in 1 upload.