1girl, armpits, black_hair, black_one-piece_swimsuit, blue_sky, blush, breasts, brown_eyes, cloud, competition_school_swimsuit, day, looking_at_viewer, matsunaga_kouyou, medium_hair, one-piece_swimsuit, original, parted_lips, school_swimsuit, sky, small_breasts, solo, swimsuit, thighs, twintails