Class 78th

Class 78th is a class batch from Hope's Peak Academy. It consists of sixteen students. This class took shelter in the old school building before Junko Enoshima erased the students' memories and put them in the Killing School Life. They are one of two batches who survived The Tragedy, the second one being Class 77-B, who faked their deaths after graduating their second year.

First Year
Class 78th had their school memories removed by Junko, leaving only one thing they could remember, themselves entering Hope's Peak Academy for the first time. It is unknown about their school lives, curriculum and teachers but it can be presumed they took part in a practical exam, enabling them to enter the Second Year.

Monokuma, during the Killing School Life, revealed to the class evidence of their school lives through certain photos, showing them taking part in swimming, athletics and various other activities, while also showing the developed friendships amongst them such as photos taken of them in the classroom and outside on the school grounds, playing in the snow.

During the Tragedy
After one year of a happy school life, the Tragedy began. At this point, it was impossible for Class 78th to continue their Second Year and Jin Kirigiri, the Headmaster of Hope's Peak Academy, suggested a plan to seal the old school building and let the students live forever inside in order to protect them from the destruction. Through video confirmation, they all agreed to the proposal and helped to seal the school until the Tragedy was over. Once sealed, they lived peacefully in the Academy for a year, unaware that the Ultimate Despairs, Junko Enoshima and Mukuro Ikusaba, were among them.

Junko soon took away the Class 78th's school memories so they could participate in her plan, the Killing School Life.

Killing School Life
The fifteen students participating in this killing game awoke in an unknown classroom, alone, only remembering entering Hope's Peak Academy for the first time before falling unconscious. They all convened in the school hall where they meet their Headmaster, Monokuma, a robotic bear under the control of Junko. Mukuro dressed up, disguised as Junko to avoid suspicion.

The class are told to follow a set amount of rules as per their e-Handbook, Monokuma also expressed that they were to live out their school lives in comfort, confined in Hope's Peak Academy forever. Since everyone had lost their memories, the situation they were placed in seemed like imprisonment rather than for their own safety. They are told the only way to 'graduate' and leave the building is to murder someone, providing they cover up their crime and evade Execution by winning a compulsory class trial as the Blackened. If the blackened succeeded, the rest of their classmates are put to death by execution, if the murderer is discovered as the culprit, then they alone are executed and the remaining participants live on, although are still confined in the school.

Many murders occurred, until suspicion began to close in on Junko thanks to Kyoko Kirigiri's probing. Seeing an opportunity to kill Kyoko in a class trial, Junko planted evidence to secure Kyoko as the Blackened for Mukuro's murder, however, Makoto Naegi takes the blame but is able to evade execution with the help of Alter Ego. Kyoko is able to save Makoto from the trash disposal room, challenging Monokuma and succeeding in forcing his hand to redo the class trial, allowing the students the opportunity to reveal everything.

During the final class trial, after the class are able to reveal their findings and real reason for their imprisonment, Junko appeared and tried to force the remaining students, Makoto, Kyoko, Byakuya Togami, Aoi Asahina, Yasuhiro Hagakure, and Toko Fukawa into despair. But Makoto convinced them to never give up on hope and Junko, on deciding she had lost, killed herself in The Ultimate Punishment.

The remaining students are able to leave the school through a vault door, readying themselves for what world awaited them although continuing to be optimistic.

Aftermath
The six survivors left the school building and looked on in shock at how the world had changed around them, surviving in this apocalyptic surroundings until being rescued by the Future Foundation, who they decided to join in order to fight against despair. The Future Foundation helped them to recover their school memories.

However, Toko wasn't accepted as a full member of the Future Foundation and instead became an intern, since Genocide Jack was considered a threat. Toko, annoyed that Hina and Hiro became members first, strove to control Genocide Jack so she could become a full member. She promised Byakuya that she wouldn't let Genocide Jack murder anyone ever again.

Upon learning of Junko's death, many members of the Ultimate Despair killed themselves, while those who did not ended up continuing their despair-inducing acts, known as the Remnants of Despair.

Kyoko is able to become leader of Future Foundation's 14th Division, Makoto, Yasuhiro, and Byakuya all being members of the same branch under her leadership while Aoi became a member of the 13th Division. Toko still remained an intern.