Hikaru's older sister was silent and withdrawn. My sister Luna is a positive, cheerful and sociable character. Even though they are twins, their personalities are very different. Hikaru admires Kouki, a famous influencer. Luna is Kouki's friend and that's SEX! “I want to be hugged by Kouki-kun!” Hikaru, the older sister decided to pretend to be her younger sister for some reason. Kouki doesn't realize it's an impersonation and gets confused, and from there, the parallel Gujuguju SEX (?) begins!