Jouji Katori (香取 譲二, Katori Jouji) is the Student Council President of Yamaboshi High School. He attempts to keep order after the student body is sent to the Isolation Dimension and are subjected to various phenomenons. Katori is a very popular figure amongst his peers and even Fujishima admires his charisma.
Intelligent, athletic and charismatic, Katori is considered a perfect student and an ideal Student Council President. There were rumors that he had a girl friend outside of Yamaboshi secondary and broke up with her. He is very confident and possesses great leadership skills, looking after and maintaining order among his fellow students while in the chaotic environment of the Isolation Dimension. However, though his intentions are always good at their core, Katori has proven willing to use any means, no matter how ruthless, if it means escaping the dimension. He spreads rumors about the StuCS to make the entire school turn against them, willing to use violence as the method to escape the Isolation Dimension, and exploited a suffering Yukina to persuade the student body to agree with his methods. He was willing to use violence when needed to control the situation such as getting the Student Council to restrain the StuCS members when they tried to talk to the students.
- Student Council: Initially, Katori merely used the Student Council to accomplish his goals and did not see them as friends. However, his view of the Student Council changed after listening to everyone's opinions in the auditorium.
- Nagase Iori: Katori teams up with Iori for the Couples Battle Royale in Precious Time and the two manage to win the tournament by a student election suggested by Iori. During the December of their third year, Katori reveals to Iori that he has romantic feelings for her, but he is turned down because Iori only sees him as a friend.
- Student Cultural Society: At first, Katori and the StuCS worked together in the Isolation Dimension to help the students who were in trouble. Soon enough however, Katori became suspicious of the StuCS, noticing how they were not experiencing any phenomenons and were too calm despite the crisis. Katori asked Kiriyama Yui to tell everyone the truth about the phenomenons and almost succeeded. After No.3 announces to the entire student body that the StuCS are the ones responsible for the phenomenons, Katori turns against the StuCS, seeing them as a obstacle in his plans. The conflict between him and the StuCS escalates when the StuCS discover his morally questionable method of escaping from the Isolation Dimension. In the end, after hearing everyone's opinion on the phenomenon, Katori agreed with the StuCS and stopped using despicable means of escaping the Isolation Dimension.
- Katori gave up his role as Student Council President during his third year. Despite this, other students continue to refer to him by his former title, and he always corrects them.