1girl, alternate_hairstyle, ass, blush, drinking_straw, feet_out_of_frame, from_behind, idolmaster, idolmaster_cinderella_girls, looking_at_viewer, looking_back, monochrome, ponytail, sakaki_imasato, shorts, sidelocks, sitting, sketch, sweat, tachibana_arisu, wet, wet_clothes, white_background