2girls, arm_up, barefoot, blue_eyes, blue_one-piece_swimsuit, blush, braid, braided_bangs, breasts, brown_eyes, day, full_body, grey_hair, hisakawa_hayate, hisakawa_nagi, idolmaster, idolmaster_cinderella_girls, kawaseki, long_hair, looking_at_another, looking_up, low_twintails, multiple_girls, on_one_knee, one-piece_swimsuit, outdoors, pool, poolside, school_swimsuit, siblings, sisters, sitting, small_breasts, soaking_feet, sunlight, sweatdrop, swimsuit, twins, twintails, water