1girl, ball, beach, beachball, bikini, blonde_hair, blue_eyes, bracelet, breast_press, breasts, cleavage, closed_mouth, feet_out_of_frame, halterneck, idolmaster, idolmaster_cinderella_girls, innertube, jewelry, large_breasts, lens_flare, lying, ohtsuki_yui, on_stomach, pien., ponytail, sand, side-tie_bikini_bottom, solo, split_mouth, string_bikini, striped, striped_bikini, swimsuit, unmoving_pattern, waves