1girl, o, arms_behind_back, bikini, breasts, cleavage, collarbone, greyscale, halterneck, hayami_kanade, idolmaster, idolmaster_cinderella_girls, koya_(koya_x_00), looking_at_viewer, medium_breasts, monochrome, navel, parted_bangs, short_hair, side-tie_bikini_bottom, solo, speech_bubble, string_bikini, swimsuit