Karen, a new teacher, was dizzy on the side of the road because of overwork. A student named Yuki happened to see his teacher collapse, so he ran to help her and took her home. The teacher was so impressed by what the student did that she invited him to stay for dinner. Yuki agreed and went for a walk around her house. He saw that she had a boyfriend and there were many photos of them in the bedroom. A moment later, a dark thought appeared in Yuki's mind and he decided to do it.