Pluto is a story about elite high school seniors, the top 1%, who are prepared to go to extremes to get into prestigious universities. June, the main character, is the high school senior. He was transferred from the general high school to the prestigious high school. The first examination result drives him to despair. One day he finds out some high-ranking students are sharing secret notebooks which contain important information. To gain the notebooks he begs the members of the secret circle. They order him to accomplish some missions to get the notebooks. In the process of accomplishing missions, he changes himself into monster. What changed the innocent boy into monster? What's happened between the students in the school?