1girl, 2022, black_hair, brown_eyes, casual_one-piece_swimsuit, cowboy_shot, electric_guitar, fender_mustang, from_below, guitar, hair_between_eyes, happy_birthday, instrument, island_lagoon, k-on!, long_hair, looking_at_viewer, nakano_azusa, one-piece_swimsuit, pink_one-piece_swimsuit, sidelocks, solo, standing, swimsuit, twintails