After episode 10 of Side
espair, Izuru is able to revive Chiaki's body, using his Ultimate Nurse, Doctor, and Scientist talents. However, since he was unable to revive her in time, Chiaki is left in a comatose state. Izuru would spends years trying to figure out why this girl interest him so much, all the while protecting Chiaki's comatose body from the chaos of the tragedy. After finding out about the New World Program, which would be in the hands of the Future Foundation, he can up with a plan to regain his lost memories and revive Chiaki's mind:
First, he would need to acquire AI Junko.
Second, he gather all the Ultimate Despairs from Class 77-B in one place, either by convincing them or forcing them. Since the Ultimate Despairs are from Class 77-B, Izuru knew an AI Chiaki would be created by Alter Ego and used as a monitor.
Next, he would contact Naegi, knowing he would be the only Future Foundation that would be willing to put them through the Neo World Program. He would then insert AI Junko into the program. AI Junko's purpose was to cause a forced shutdown and rewrite the Neo World Program so that the data of AI Chiaki and the Ultimate Despair that killed would be saved. Evidence of this is the "deceased" character appearing while the program was glitching, AI Chiaki appearing within Hajime's mind, and her final goodbye at the end DR2.
After the force shutdown Izuru would have both the memories of both Hajime and Izuru, the data of AI Chiaki and the other "killed" Ultimate Despairs, and the technology of the Neo World Program in his possession. Using the the comatose Ultimate Despairs as guinea pigs, he would figure out who to use the Neo World Program to restore a brain dead person.
Finally, he would retrieve Chiaki's body and use his finding to upload the data of AI Chiaki and original Chiaki's memories into her comatose body, ultimately reviving her mind.