Mukuro, Junko, and Izuru stood atop a tall building near the school, with a clear view of Class 77-B's room. She then walked into the airport and waited for her sister Mukuro, while narrating her plan to the viewer and her sister. However, he ends up getting killed by Junko in a fit of despair, as he is one of the few people she cares about the most. Ss she observed the massacre taking place on the security cameras, Junko talked about how she believed that despair could make life more interesting.
Junko replied that it was, but that she already got bored of it, as she drew a picture of Monokuma. Junko's "moods" included (but were not limited to) her Monokuma persona, sickening cuteness, severe depression, clinical sophistication, boisterous vulgarity, eerie stoicism, and haughty superiority. Junko explained that the two of them had been scouted by Hope's Peak Academy and that they would be attending school there. Junko has the ability to cause nearly anyone to fall into despair, and she revels in the despair felt by herself and others.
In (chronologically) earlier installments of the series, such as As a young fashionista, Junko is described as simply "not fake", charismatic and eager to try new things. Because of that, she took an interest in despair, which she believed to be unpredictable and exciting. Because hurting people close to her will cause her greater despair, she tends to deal with them in more personal ways; for instance, she personally killed her sister Mukuro and her love interest Yasuke, making them both believe she did not care about them at all during their last moments, and later treating their bodies in very disrespectful manners. Makoto states that she doesn't need to die, but Junko executes herself even after his request. Junko watched the class through her binoculars before proclaiming that they would infect the world with despair. Junko had a somewhat complicated relationship with the homeroom teacher of Class 77-B.
A student labeling herself as the Ultimate Fashionista, it is soon revealed that she is the founder of the organization known as "Ultimate Despair", a terrorist organization responsible for "The Worst, Most Despair-Inducing Incident in the History of Mankind" and also the true identity of the bear that oversees the game, Monokuma.
She is very popular among people and students in Hope's Peak Academy; even the In the original Japanese, Junko's title is Super High School Level Gyaru (超高校級の「ギャル」). As the trial carries on, Makoto, Kyoko, and Byakuya Togami appear in the game and Junko's full plans are revealed to the cast. The children started to call themselves the Junko's classmates, the 78th Class, sealed Hope's Peak Academy and lived peacefully inside it for a year without knowing that the Ultimate Despair members were already in their midst.
The Warriors of Hope started to kill adults, even their parents, in order to create a paradise for children. During the course of events, Junko was able to ensure the deaths of several of the students, before realizing that Junko almost succeeded in her attempt to kill Makoto and frame Kyoko, but was ultimately fruitless when Kyoko saved Makoto just as she was about to stab him, and then by Makoto not calling out Kyoko's lie during the With Kyoko's lie not called out, a frustrated Junko had no choice but to call guilt on Makoto, who remained under unconvincing suspicion throughout the trial. Out of fear of being outed, Juzo agrees and Junko flees back to her hideout. The Despair Sisters assembled the Student Council, intending for them to kill each other. However, Makoto reassured the surviving students of a future ahead despite the difficulties, and thus was able to convince all the students to vote for “Hope”, condemning Junko to a final defeat in the climax of a Though seemingly livid over the results shortly after the vote was settled, Junko instead became perversely delighted as she realized she would be able to experience the extreme despair of painful, unnecessary death. Junko remained calm during these events and was amused by how much Nagito believed in hope. However, Junko had already planned ahead and had murders occur in the school. As children, Junko and her twin sister Mukuro lived in abject conditions and were even homeless at one point. While he was sitting on a bench in front of the remains of the sand sculpture, Junko ran up to him with a large smile and whispered in his ear that she was the culprit who destroyed the sculpture all along, asking him to keep it a secret. For the first time in his life, Yasuke cried in front of another person, after making her promise she won't make fun of him, won't tell anyone and won't try to console him. She feared her sister's killing abilities may have become rusty since she had just returned to Japan, but it seemed that such was not the case.