The Japanese manga and anime series Future Diary (未来日記, Mirai Nikki), written and illustrated by Sakae Esuno, features an extensive cast of characters. The plot depicts the Diary Game, a deadly battle royal between 12 different individuals who are given "Future Diaries," special diaries that can predict the future, by Deus ex Machina, the God of Time and Space, with the last survivor becoming his heir.

The series follows Yukiteru Amano, a socially awkward boy and one of the game's competitors who only wants to survive. Yuno Gasai, another player of the game and a friend who would do anything to be with Yuki. Minene Uryū, an infamous terrorist with a grudge against God, and Aru Akise, a genius teen detective and a friend of Yuki, who investigates the true purpose of the game and Yuno's dark secrets.

Future Diary Holders are based from the Dii Consentes or Twelve Olympians in Roman and Greek mythology.

Yukiteru Amano (天野 雪輝, Amano Yukiteru) is the main male protagonist and hero of the series and the First Diary user. Also known as Yuki (ユッキー, Yukkī), he is a reclusive and shy 14-year-old middle school student, opting to be a bystander to incidents around him to write about them in a diary on his cell phone instead. He becomes involved as one of 12 contestants in a 90-day battle royale when, to his shock, his imaginary friend Deus turned out to be a real God of Space-Time, planning to have the sole survivor of the game succeed his throne. Yuki's ordinary diary becomes the Random Diary (無差別日記, Musabetsu Nikki), a diary capable of predicting future events happening around him from his point of view. While versatile in any situation, the diary does not state what happens to Yuki himself, and since it is written from his point of view, the entries may not always be accurate.

Unlike most of the contestants, Yuki wishes for a simple, peaceful life. Because Deus considers him a personal favourite to win, he is mainly targeted by other Diary users. Knowing he is weak, cowardly and naïve, he quickly makes friends and allies. One of these is Yuno Gasai, an obsessive stalker who is madly in love with him and will kill to protect both of them. His goal is to not kill anyone; however this outlook has changed when his divorced parents are killed because of the game and Yuno convinces him that becoming the God of Space-Time can bring them back, becoming a ruthless and dishonest player.

Eventually he learns of Yuno's true origins and intentions, finally stepping out of his role as a constant bystander to intervene in changing her future, including those of the other Diary owners that led terrible, unfortunate lives. When trapped by her in an illusionary utopia, he breaks free through his love and force of will to meet her again. A touched Yuno commits suicide to let him win the game. A distraught Yuki refuses to use his godly powers for 10,000 years, until the Third World Yuno returns to him with memories and love of the First World Yuno. as they become the gods of the third world, succeeding Deus without another death game involved.

He is named after Jupiter, the Roman god of the sky, weather and lightning.

Yuno Gasai (我妻 由乃, Gasai Yuno) is the main female protagonist and antagonist of the series and the Second Diary Holder. While a perfect model student on the surface, she is actually a psychopathic villains yandere who is obsessed with Yukiteru Amano, whom she affectionately calls "Yuki", and kills unhesitatingly to protect him. Her Future Diary is the Yukiteru Diary (雪輝日記, Yukiteru Nikki), a stalker diary that gives her explicit details on whatever Yuki is doing in the present 10 minutes. By working together with his Random Diary, they are able to solve their diaries' weaknesses.