Nee, Mou Isso Tsukiacchau? Osananajimi no Bishoujo ni Tanomarete, Camouflage Kareshi Hajimemashita

Masaichi Mazono, an otaku boy, and Toiro Kurumi, the most beautiful girl in school, are childhood friends. Toiro, who was always in Masaichi's room, was supposed to be like family to him. But one day, Toiro, who was constantly getting annoyed by her romantic troubles, asks Masaichi to play the role of her boyfriend. They thought it would be simple to pretend to be a couple because they'd been together for so long, but their ideal childhood friend can't possibly end up as a false lover... "E-eh no, holding hands is embarrassing." A childhood friend who is more than a lover embarks on a more adventurous lover's life than she could have dreamed! (Source: Hobby Japan, translated)