Sukebe no Seishun
I didn't read it carefully. But catch the idea of what's going on. Good but not a fan of it. Some parts uncensored.
Romance Debut!!
Taller most likely seme Shitara x shorter with high school debut look uke Yuzuki. Yuzuki's friend circle is protective over him. When Toyo thought Shitara was bullying him he stood up for the uke to protect him. Shitara was in love with yuzu since their high school preparation cram school days. Since uke was rejected by the girl he like at cram school seme got an opportunity to be with him. And they ended up together. Shitara's older sisters are giving him advices about how to treat a girl and training him was paid off and his sisters are such beauties. They got it right away when they guessed correctly about they are going out. And Yuzuki has all his dream types.
Sugar Dog Life