|Spoiler warning: Plot or ending details follow.|
Recollection: A Diary is the twentieth episode of the Guilty Crown anime. It first aired on March 8, 2012.
Mana has almost taken control of Inori's body and Gai tells his father, Shuichiro, that the Apocalypse will be coming and announces it to the world that the Leukocyte will destroy Earth on December 25th. The remnants of the Undertakers and the Kuhouin Group escape Japan on a ship along with the students of Tennouzu where Shibungi, who was released by Gai, gives Shu a journal by his father which reveals the Apocalypse virus histroy.
In 2013, Shuichiro was a Professor researching on Genomic Resonance and befriended Shu's father Kurosu, who the latter was interested in the former's work. In 2017, Kurosu meet his future first wife, Saeko Shijou, a fellow colleague whom he marries after she became pregnant with their first child, Mana. But in 2022, a meteorite crashes on Earth and was discovered by Mana and Saeko. Shuichiro and Shu discovered a virus inside the meteorite which reacts when the Genomic Resonance was used.
Their research gets them the attention of the "Daath" organization in 2023, who's representative, Yuu, offers to help them as they have been waiting for coming of the virus as it will start the Apocalypse. Furthermore the virus has begun infecting Mana and Saeko, which the former is becoming insane while her mother is slowly dying by the crystallization and is pregnant with Shu. Yuu orders Kurosu to not abort the baby as Mana has chosen Shu as her mate where they will start a new race after the Apocalypse. Saeko dies giving birth to Shu which sends Kurosu into grief that he refuses to work with Daath anymore. Shuichiro, jealous that Kurosu's children will be the originators of the new human race, joins Daath by helping them find a suitable mate for Mana by experimenting on children with the Apocalypse virus.
In 2028, Kurosu, who have since kept busy on finding a cure for the virus, falls in love with his new assistant, Shuichiro's sister, Haruka, who also takes care of Kurosu and his children, eventually marrying him. At the same time, Gai, a victim of child trafficking, is adopted by Shuichiro who also subjects his stepson in his experiments which eventually lead Gai to run away and get rescued by Mana and Shu. On the day of the Lost Christmas incident, Shuichiro learns that Kurosu manage to find a cure for the virus by creating the Void Genome but wants to keep the burden creating it on himself. But a bitter and jealous Shuichiro thinks Kurosu is looking down on him, kills Kurosu and steals his research before Haruka finds her husband's body.
In the present, Haruka reveals that Mana was able to enter Inori's body during the 2nd outbreak and slowly taking control of her because the voids Shu have been extracting are pieces of Mana herself. Before Shu joins a joint attack on GHQ with the Undertakers, the Kuhouin Group and a PMC, he tries to give back everyone's voids since they will die if he dies as well but they refuse and Shu forgives Souta for betraying him.