ねぇ、もういっそつき合っちゃう?幼馴染の美少女に頼まれて、カモフラ彼氏はじめました (Series) favorite_border

Volume 1 synopsis: Masaichi Mazono, a self-proclaimed otaku, and Toiro Kurami, the most beautiful girl in school, are childhood friends bound together by years of shared history. One day, fed up with the drama that comes with relationships, Toiro asks Masaichi to pretend to be her boyfriend. "We're already together all the time, so playing a couple should be easy!" they both think — but there's no way a perfectly matched pair of childhood friends is going to stay fake lovers for long...!?