Older sister Hikaru is quiet and withdrawn. Her younger sister, Luna, is cheerful, bitch and gregarious. Even though she is a twin, her personality is so different. Her idol of Hikaru is Kouki, a popular influencer. Luna is that Kouki and SEX friend! "I want to be held by Kouki-kun!" Hikaru, her older sister, who ended up pretending to be her younger sister. Kouki doesn't realize it's an impersonation and gets confused, and from there, parallel (?) Gujuguju SEX begins!