Deus is a mysterious entity in the Future Diary -Another:World- drama series. They replace the original Deus Ex Machina in the drama continuity. It is unknown if Deus is, in fact, a deity, although they similarly serve as the host of the Survival Game.
It is later on revealed, that "Deus" is really a virtual reality program named "Olympia", which was created as a new method of treatment for coma patients gone horribly wrong.
Deus appears as a holographic purple emoticon resembling a smiling sun.
In their human form, they take the appearance of a woman with light-brown, shoulder-length hair, wearing a short black dress and black high-heels.
Deus seems to view normal human life as quiet, boring and not worth taking into consideration. They refer to such lifestyle as worthless, evident in how they seem to be indifferent about the lives being lost in the game. They instead consider the survival game as a much better way to define one's future.
However, despite all this, they genuinely love humans (or more precisely their patients) and wish for nothing more, than to create a perfect world for them and make them happy.
They explain the rules. There are seven Diary Holders and they must kill each other until one remains. The only way to stop a Dead End is to kill the one with a Diary who triggered it, and if a Diary is destroyed its owner disappears. The time limit is a mere month. The winner will have a wonderful future, namely, a new future diary and what is written in this Diary will happen and it will come to pass as they see fit. And encourages the participants to steal each other's future before they disappear themself.
When Arata finds out the truth about the survival game and enters Olympia again, with the Release Code to stop Deus, they lure him to them and confront him in their human form. Deus explains to Arata that Olympia isn't perfect yet, that it needs a "last piece" to work properly, without it, time in the virtual world simply goes into a loop of one month. The Survival Game was created by Deus to find out, which one of the participants had the strongest will to live and use the winner as said "last piece". They say that Arata has disappointed them since he was so close to winning the first game, but was killed by Yuno Furusakis AI before he could truly finish it. Deus gives Arata two choices: choose the real world and use the release code, which would shut Olympia down and send him and the others back to the real world, where he'd still be comatose or to choose the virtual world, stay in Olympia forever and become the "last piece". To their surprise and anger, Arata chooses the real world, saying that he will go back together with Yuno. Deus says that Arata has once again disappointed him and leaves.
They are later on seen observing Rui, seemingly having chosen him as the last piece instead. They use some sort of a brainwash on him, ordering him to "remove" Hoshino Arata. When Rui fails to do so, Deus angrily states that he is useless and has no soul, killing him afterward by destroying his future diary. They then start a new survival game containing Yuno, Tohru Kibe, Haruna Okie, Megumi Fuwa and Kinjiro Hagito. But Yuno manages to foil their plans, by convincing the others not to let themselves being manipulated by Deus.