This story follows four friends, and particularly Irisu Kyouko. 
As a child, Irisu grew to fear making connections with others. In elementary, she gravitated to U-Tarou, the school rabbit. One day, she finds this rabbit's decapitated head in a pool of its blood, being licked by a cat, causing her to grow to hate cats. In reality, it was a young Uujima who found the rabbit dead, and decided to behead so "it would be remembered", since he had watched Irisu play with U-Tarou many times.