Read manga: Triangle Struggle

manga
Genres: Comedy ; Romance ; Yuri
Artists: Kamotama
Status: completed
Summary:

Hikaru finds her little sister Akane irresistible, while Akane sees her big sister as nothing but a worthless pervert. Meanwhile, Hikaru's friend Shinobu, subtly vies for her (Hikaru's) attention while trying to help her deal with her siscon ways.