U-tarou is the bunny that was the school's pet rabbit who had passed away, only to get decapitated by Uujima. In the game's images, it's shown to be all white and missing an ear.

U-tarou was not very well liked by the school, likely due to its scruffy appearance. Most students preferred playing with the school's pet cat, causing the bunny to be left alone and neglected the majority of the time. The only person who really looked after it was Irisu Kyouko, who couldn't play with the cat due to her allergies.

A haunted image of U-tarou

A common theory with U-tarou involves the rabbit actually taking control of Irisu, wanting revenge against Uuji. This is supported by the red and black color schemes seen on Irisu's face frequently, and the image obtained for gaining 100,000 points.