The Data Migration is an OVA that tells the events after the end of the anime. It includes the missing material from the end of the manga as well as more complete information of the events in Future Diary Redial centered around Yuno's 3rd incarnation.
Summary[]
Muru Muru is imprisoned by her 3rd incarnation but not before absorbing the memories left of the dying Yuno.
Due to the changes in the future, Yuno's family is now a normal and happy family, and Yuno is a normal teenager herself. Third World's Kurusu's son was spared of death due to Second World's Minene Uryu's intervention by calling him to warn him of his son's cardiac condition before he suffered symptoms. She is happily married to Third World's Nishijima and has two children.
While everything seems to be nice, Third World Yuno starts to have flashes of memory regarding a certain person that she cannot remember, but she feels that person is important and thus is sad.
The intervention in the future has made Deus Ex Machina forsake the Survival Game, since Third World John Bacchus learned the original version of his game would result in his death. Instead, Bacchus attempts to create several new games, but is serially rejected and finally expelled by Muru Muru who is bored of seeing games in which Bacchus gets an unfair advantage.
Deus asks Second World Minene to be the next god in the third world, but she refuses the offer, stating that she's happy with the life she currently has and that they were "two other problems."
Yuno is seen talking with an unknown individual regarding the memories that have been haunting her, but gets no definitive answers, save that the person she remembers is indeed important to her.
Muru Muru detects an anomaly in the space-time-continuum, but neither she nor Deus can understand the cause.
Yuno is friends with Hinata, Mao, Ouji Kosaka and Akise Aru, and they spend a fun time in the beach. Yuno experiences periods of flash-backs where she experiences the same greeting from Hinata and Mao more than once. Akise Aru is secretly an observer sent to keep a close eye on Yuno and on other possible anomalies that may occur. Yomotsu Hirasaka is still a vigilante during night and a shop owner in day selling merchandise of his vigilante self. His shop is visited by Yuno and the others, and finds much to his chagrin that his vigilante self is considered a freak.
Ai Mikami and Orin Miyashiro work for Tsubaki Kasugano and attempt to secure Akise as per her request as she has romantic feelings for him. Things take a turn for the worse, however, when they confuse Akise for Ouji, as Tsubaki hugs him and realizes the truth, she screams in terror prompting Ouji to escape.
Eventually, Yuno begins to feel each time more and more worried about the recurring memories, and talks with the mysterious person more often. Eventually, Yuno reaches the alternate dimension of Deus and begins to search for clues. Muru Muru discovers her and pilots a giant mech in order to prevent her intrusion. However, Second World Minene appears to back up Yuno and tells her to send her greetings to "him".
Yuno goes on her way but is interrupted by Akise on the way. Akise claims he will not let Yuno go, because she and her other incarnations have been a problem for him, as well as his own personal feelings for Yuki. Yuno refuses to retreat as she wants to know the truth, and he attacks her with a sword. The two briefly engage with Yuno easily managing to pin Akise down and claims she does not care about his feelings and that she will meet the person that has been calling her. Akise no longer impedes her passage and asks her to send his greetings to "him".
Yuno goes on and she find a big spherical room similar to the one Yuki was imprisoned in by Yuno beforehand. Muru Muru attempts to stop Yuno but Deus stops her, trying to see if she can change the future. Yuno meets the first incarnation of Muru Muru who is revealed to be the person trying to contact her. It is revealed by Deus that because Muru Muru absorbed the feelings and memories of Yuno's first incarnation for so long, these have been affecting Muru Muru, causing her to contact Yuno in order to give them back to her. Muru Muru succeeds in passing them to Yuno through the fragment of Deus.
Yuno then proceeds to smash the spheric room, which opens a rift into the second world, causing her and Yuki to finally meet. Yuki is surprised and happy to see Yuno. He asks Yuno how she did it, but Yuno insists that they leave this discussion for later and instead go to see the stars together.