Below is a list of characters that appear in the Future Diary universe.
Yukiteru Amano (The First)
- Yukiteru Amano (天野 雪輝, Amano Yukiteru) sees his own life as if he were a bystander. His "Random" (Indifference) diary reflects that attitude. In a detached, neutral tone, the diary records the future changes in his surroundings every couple of minutes. This gives Yukiteru timely, detailed entries of the future around him and is perhaps the one of the most accurate diaries revealed so far. It is extremely versatile and useful in just about any given situation. Its only flaw is that nothing short of a Dead End will make the diary record anything about Yukiteru himself.
Yuno Gasai (The Second)
- Yuno Gasai (我妻 由乃, Gasai Yuno) is hyper-obsessively in love with Yuki, as one can safely guess from just the simple name of her future diary. His condition and actions are recorded every ten minutes in her "Yukiteru" diary while also providing small commentary made by Yuno in some of the entries. Its most obvious weakness is that it does not show Yuno's future at all — her condition, situation, or surroundings — unless it somehow involves Yuki or her own Dead End. Working with the First's "Indifference" diary, however, covers both of their diaries' individual flaws; as it has been said, the two make for a perfect combo, both in theory and in practice.
Takao Hiyama (The Third)
- Takao Hiyama (火山 高夫, Hiyama Takao) is a teacher in Yuki's school and is the serial killer reported within its vicinity. His "Murder" diary records the location of his next intended victim. It is a handy diary if one knew the true identity of the other diary holders and wishes to take the offensive in the game, but it does little in the way of anything else. He was the first to die in the Survival Game.
Keigo Kurusu (The Fourth)
- Keigo Kurusu (来須 圭悟, Kurusu Keigo) is a police officer, so it follows with reason that his diary relates to his work. The "Investigation" diary gives Keigo information of future crimes and activities committed anywhere within the prefecture he is assigned to. Whether or not this means his diary can record events that will happen simultaneously in different locations is still up in the air. Its major flaw is a location issue; his diary is rendered useless at predicting anywhere outside his patrolling district.
Reisuke Houjou (The Fifth)
- Reisuke Houjou (豊穣 礼佑, Houjou Reisuke) is a seemingly harmless five-year-old child. Accompanied by some drawings, his "Super Vision" diary is a coloring book that gives a small summary of the activities he will perform for the day. However, not only is there a large time gap between the entries, the diary only shows three of them per day: morning, noon, and night. It does have a certain advantage of giving Reisuke all three entries at the same time, which allows him ample time to carefully plot his next move, as well as some pictures drawn by him, giving him some source material other than writing.
Tsubaki Kasugano (The Sixth)
- Tsubaki Kasugano (春日野 椿, Kasugano Tsubaki) is a maiden and figurehead of the Omekata religion. Her "Thousand League Eyes" diary is unlike the other diaries, as it is a scroll, rather than a cell phone. As its name would suggest, it is able to report the future of all her followers; allowing her to gain some form of mind control over them. Unlike Yukiteru's diary, it is not limited to just her surroundings, but sees far-off events; ones that lie a great distance away from where she resides. Her diary can also record near-future events; those that will occur after only a few seconds ahead from the present. This provides Tsubaki with massive amounts of information to work with. However, it can pose as a hindrance in times where a situation changes constantly or when she needs to react quickly to incoming threats.
Marco Ikusaba and Ai Mikami (The Seventh)
- Marco Ikusaba (戦場 マルコ, Ikusaba Maruko and Ai Mikami (美神 愛, Mikami Ai) were originally thought to be more apprentices of the Eighth at first; Marco's apprentice diary predicted attacks before they happened, while Ai's located who ever she was looking for. In chapter twenty-eight they revealed themselves as together being the Seventh diary holder as well. The powers of their diaries, together known as the "Exchange" diary, are operated by two separate cellphones. It does appear their diaries are not affected by disruptions in the cell phone network as Akise's jamming plan only causes them to discard their Apprentice Diaries from the Eighth and use their own.
Kamado Ueshita (The Eighth)
- Kamado Ueshita (上下 かまど, Ueshita Kamado) is a large, strangely shaped woman in charge of an orphanage named "Mother's Village". Kamado's diary seems to be in the form of a website where she can rent out blog space to others and can automatically promote its users' rank based on the number of posts the user makes. For instance, Ouji Kousaka, in chapter twenty-five, submits enough entries to be promoted from "commoner" to "apprentice diary holder". The latter rank appears to give users the same abilities that the original diary holders possess without the drawback of the user dying if his or her diary is destroyed. The only apparent problem with this diary's effects is that the apprentices have to stay connected to the server, or else they will lose use of their diaries.
Minene Uryu (The Ninth)
- Minene Uryuu (雨流 みねね, Uryū Minene) is a terrorist bomber. Like the Fourth, her "Escape" diary goes along with the type of profession she is involved in. Whenever Minene faces a dire situation, the diary will chart out the best course of actions she can take in order to get out of a tight spot. Based on the function of her diary, it might even help reduce the chances of her receiving a Dead End, and it is probably one of the best diaries to have in Deus' game of survival. The diary's only shortcoming is that there are some circumstances where the odds are too heavily stacked against Minene to the point where the diary won't be able to secure an escape route for her.
Karyuudo Tsukishima (The Tenth)
- Karyuudo Tsukishima (月島 狩人, Tsukishima Karyūdo) loves and values his dogs more than himself; as shown when he cooked them steak and give them thirty-year-old wine for dinner, while he himself was content with eating cup ramen. He is the owner of the "Rearing" diary, which allows him to check on the status of his beloved dogs and control them in squads via voice commands. The dogs can be used to chase and kill people. The diary's weakness seems to be issuing the order of chasing multiple targets, which would require greater concentration in herding the dogs and would also leave the user vulnerable to attack as the holder would be alone.
John Bacchus (The Eleventh)
- John Bacchus (ション バックス, Jon Bakkusu) is finally revealed in chapter thirty-six as the mayor of Sakurami. He uses his influence to take down the other diary holders. His Diary abilities have yet been detailed yet so far with its power he has been able to counter everything thrown at him, unless for unexplained reasons if Masumi is involved, described as the Watcher Diary, this and its inability to predict Masumi the only person who involved who didn't have a Diary may mean that his power is to read other peoples Diaries. However, he is able to move the voters with his words alone to demolish Mother's Home and even convince Deus to remove the First and Second because of their absences. His true goal has later been revealed that he wished to use the 8th's diary to hook up with a super computer, given everyone in the city the potential to becoming a Apprentice Diary Holder to hope to make a new and great kingdom that he will rule, probably a ruse to ensure his winning the game as giving everyone a Diary means he can access all their information the same way 6th could with her diary. Interesting, the Eighth considers him to be a gentleman.
Yomotsu Hirasaka (The Twelfth)
- Yomotsu Hirasaka (平坂 黄泉, Hirasaka Yomotsu) is a blind man who makes use of a tape recorder that he dubs the "Justice" diary, where it records the wrong-doings of future events he thinks need correcting. It's a pretty misleading name since Yomotsu considers the evil deeds committed by a religion cult as much of an injustice as finding random trash on the floor. His diary's functions are actually similar to the Sixth's "Thousand League Eyes," but rather it's the Thousand League Hearing. He is able to create illusions using hypnosis granted by his diary.
Azami Kirisaki (The Thirteenth)
- Azami Kirisaki (霧崎あざみ, Kirisaki Azami) is the thirteenth diary owner who only appears in the PSP visual novel, Future Diary: The 13th Diary Owner and the Main Protagonist of Future Diary: Grand Battle. Her diary is the "Video" Diary, taking the form of a video camera which shows what will be recorded on it. She is shown wearing a school uniform and a yellow, hooded raincoat. Her beloved baby sister Kasumi Kirisaki was hospitalised by Takao Hiyama.
- Deus Ex Machina (デウス エクス マキナ, Deusu Ekusu Makina), the god of time and space, is Yukiteru's supposed imaginary friend and the mastermind behind the game. He is looking for a successor, which is why he gave future diaries to twelve candidates and placed them in a game of life and death. He seems to favor Yukiteru the most out of all the other candidates as his next possible successor due to the miracles Yukiteru is able to pull off, not paying attention to the fact that Yuno is helping him. In chapter twenty-four, it is revealed that, despite being a god, his lifespan is coming to an end, thus there has to be a replacement.
- Muru Muru (ムルムル, Murumuru), Deus's servant, is often seen with the eliminated candidates in omake panels. As of chapter twenty-four it is revealed her favorite is Yuno Gasai, and she is betting on her to win the game. Murumuru also admits to having a hand in the Fourth's death to speed things up. She has a rather playful and nonchalant attitude toward Deus despite his warnings to her. In a spin-off series she accidentally destroyed Yuno from existence, so she currently has taken Yuno's place as the Second till the damage can be fixed.
- Rea Amano (天野 礼亜, Amano Rea), Yukiteru's mother, is rarely at home because of her work as a video game programmer. Despite this, she maintains a very casual and close relationship with Yukiteru and approves of Yuno as a potential bride for her son. She later dies in chapter thirty-three after Kurou stabs her with a knife while trying to drag him to the police.
- Kurou Amano (天野 九郎, Amano Kurou), Yukiteru's father, is divorced with Yukiteru's mother due to a debt amounting to three million yen which he could not pay. Initially, he appears in chapter thirty claiming to just want to check on his son, but it turns out that he has only returned to destroy Yukiteru's diary in order to fulfill a deal with the Seventh. Despite his only clear desire being to free himself from his debts, he does try to save Yuki when the latter almost falls to his death, but takes the parachute away from Yuki before the tower crumbles soon after. He then stabs his wife when she tries to take him to the police and escapes, though is stabbed to death himself two chapters later by the Eleventh's men.
- Moe Wakaba (若葉 萌絵, Wakaba Moe) is a girl that appears in a flashback in chapter 34, in which she turns down Yukiteru after he gives her a love letter.
- Ouji Kosaka (高坂 王子, Kōsaka Ouji), another one of Yukiteru's classmate, is in Yuki and Yuno's classroom during the previous semester and is one of the first people to betray him during the terrorist bombing incident. He writes down a list of all of his proudest accomplishments in a blog he dubs the "Kousaka King Diary", often using the phrase "I'm Shining!" after each sentence. Due to having blogged many times on his cellphone, which is connected to the Eighth's diary, he becomes a "Diary Holder Apprentice". His diary helps him save his friends, but since it does not reveal what is happening around him, Yuno is able to shoot him with a crossbow. Since he is inadvertently working as the Eighth's spy, Yuki destroys his diary in chapter twenty-seven, though does not die because it was not a true future diary.
- Aru Akise (秋瀬 或, Akise Aru), a classmate in Yukiteru's school, dreams of one day becoming the world's greatest detective. The student detective is able to correctly deduce the culprit behind the serial dog murders even before the police. He is mistaken for being a future diary holder due to his quick wits and superior deduction abilities. His physical prowess is nothing to scoff at either as he is able to overpower and out maneuver a psychotic Yuno at one point. He has included himself into the investigation of the Diary Holders and works with Masumi and Minene.
- He is the main character in a spin off series where Muru Muru accidentally erased Yuno from existence, which means she did not save Yukiteru from the Third's attack. So until the damage is fixed, Aru, along with Murumuru, take the place of the First and Second. Murumuru suspects he is homosexual because of his strange actions around a recovering Yukiteru.
- Hinata Hino (日野 日向, Hino Hinata), Karyuudo Tsukishima's daughter, is aware that her father is instigating the carnivorous hound attacks. In order to shake off suspicion from her father's pursuer, she accepts the "Rearing" Diary and uses it in her father's place. Hinata is a classmate in Yukiteru's homeroom and is the first person to reach out to him and become his friend. In chapter twenty-nine, she is treated for knife wounds inflicted by the Seventh.
- Mao Nonosaka (野々坂 まお, Nonosaka Mao), another one of Yukiteru's classmate, is good friends with Hinata and is a willing accomplice in Hinata's scheme to kill Akise Aru. After the carnivorous hound incident she becomes friends with the group. It is implied that she has feelings towards Hinata, which is later confirmed in chapter 41 through her Apprentice Diary. Hinata apologizes for using Mao's feelings during the aforementioned incident. She is later treated for knife wounds inflicted by the Seventh.
- Masumi Nishijima (西島 真澄, Nishijima Masumi), Chief Investigator and Keigo's subordinate, is part of the investigation team assigned to protect Father Haiman from the terrorist, Minene. Masumi had feelings for Natsuko and, much to Minene's confusion and dismay, would take every opportunity to ask "her" out for breakfast, lunch and dinner. He is then seen as the Ninth's informant and is assigned by the Mayor of Sakurami (the Eleventh) to be his bodyguard. He works with Aru to figure out the true identity of the third corpse found in Yuno's residence and later helps the Eleventh and the Eighth escape from Yukiteru and Yuno. However, he is really working for Minene and Akise, and even proposes to Minene at the end of chapter 39.
- Natsuko Ooshima (大嶋 夏子, Ooshima Natsuko), a rookie detective who was part of the Investigation division, was killed by Minene so that she can assume the rookie's identity and infiltrate Sakurami Police Station undetected.
- Orin Miyashiro (宮代 お鈴, Miyashiro Orin), an assistant to Kamado Ueshita. Works as an assistant at the Mother's Village orphanage.
- Tarō Nanba (難波 太郎, Nanba Tarō) - frequently nicknamed Ta-kun, an orphan living in the Mother's Village orphanage. Companions with Marco Ikusaba, Ai Mikami and Orin Miyashiro.
- Ryuji Kurosaki (黒崎 竜司, Kurosaki Ryuuji), the secretary of John Bacchus. He aids John in his attempt to win the Survival Game. He possesses the Secretary Diary, which predicts the effects of John's actions.
- Funatsu (船津, Funatsu), the second-in-command of the Omekata Religion. Chiefly responsible for assassinating Tsubaki Kasugano's parents, which allowed him to preserve his position in the cult. He forced Tsubaki to become a sex slave for the religion, which eventually drove her to the point of insanity.