idolmaster, idolmaster cinderella girls, shibuya rin, dokuro-san (artist), monochrome, sketch, 1girl, anus, ass, blush, bow, bow panties, cardigan, character name, from behind, hand in pocket, jewelry, leaning forward, long hair, looking back, multiple views, necklace, necktie, panties aside, pantsu, pleated skirt, pubic hair, school uniform, skirt, skirt lift, spread anus, underwear, viewed from below, x-ray