Shirime (尻目, Anus Eye) is a strange yokai with an eye popping out of his butt.
Long ago, a samurai was walking at night down the road to Kyōto, when he heard someone calling out for him to wait. "Who's there?!" he asked nervously, only to turn around and find a man stripping off his clothes and pointing his bare buttocks at the flabbergasted traveler. As if this weren't traumatizing enough, a huge glittering eye then opened up where the strange man's anus should have been.
The samurai ran away screaming, and this obscene apparition was never seen again.