Nee Summer!2 -Nee-sama- by Artemis - Adult Sex Game

Yuta Yamauchi and Kei Higashide became a couple on a sunny day. The two started living together and lived in peace, but Yuta's sister and Kei's nemesis, Otoha Yamauchi, came over. When Otoha learns that his younger brother lives with Kei, she refuses to recognize the relationship between the two and comes up with certain conditions. Yuta and Kei struggle together to get Otoha's recognition.