A Future Diary is the main tool used in the Future Diary series and is its namesake. It has the ability the future in several ways, and it is mostly used by the participants of the battle royale set by Deus Ex Machina, the God of Time & Space. They work similarly in the Future Diary -Another:World- series.
Overview & Background
The Future Diaries are tools created by Deus and John Bacchus who sought a way to achieve further human evolution. The result of such project are the Future Diaries, that can read the future, doing so in several ways and have several forms as well. The most common form is a cell phone, in which people write entries, however other forms exist, such as a picture book, or a recording device, etc.
As mentioned above, each diary reads the future in a different way, this as a result that each Diary reflects its Holders, in terms of personality, traits, desires, etc. For the sake of Deus's game, the Diaries have strengths as do have weaknesses, for example one can read the future about others, but not of oneself, this means that if an attack is aimed at one's person, that person will likely not know how and where will the attack come from, leaving a vulnerability that must be solved by the Holder itself.
Despite the differences between the diaries, there are things that most of them have in common. One is that when an user uses the diary to read and otherwise change the future in any way, this will have an effect in reality, changing what would have happened in normal circumstances. When this happens in "battle" amongst Holders, entries in the diaries are changed as to cope with the changes done in the future, this specially in the cell phone diaries is known via a signature sound (similar to a Noise found on televisions). When this happens an entry known as a Dead End may appear. This entry means that given the changes on the future, if allowed by, the Holder will be killed. Although a Dead End is not impossible to overcome, the chances to successfully do so vary a lot, although it is usually very difficult. Another entry that is known to appear (albeit only shown in one diary) is the Happy End, an entry that shows when the Holder will be successful in his or her goals.
It appears that each diaries ability are also based on what the holder used to write about in there old diaries, example: Yuki's future diary can only tell what is happening around him,in his old diary he use to write about the things that were happening around him. If this is true, then that means Yuno wrote about Yuki every 10 minutes, the third might have wrote about his past victims, the fourth wrote about his investigations, the fifth may have wrote only 3 entries a day, the sixth could have been writing about the cults activities, the sevens most likely wrote about each other, the eighth wrote about the orphans, the ninth wrote about her actions and here plans most notable her escape, the tenth most likely wrote about his dogs, the eleventh possibly wrote about people or what business he has conducted, and the twelfth wrote about the deeds he thought were righteous.
A Diary Holder is a person capable of predicting the future via his or her Diary. Primarily, there are twelve Diary Holders who are candidates for Deus Ex Machina's survival game (Thirteen in the game, The 13th Diary Holder). However, it is possible to create Apprentices where each individual receives a future diary as well.
List of Diaries
The following is a list of the diaries used by the main characters and participants of Deus's battle royale.
- The Random Diary (無差別日記, Musabetsu Nikki?): The diary used by the series's protagonist Yukiteru Amano also known as The First. It gives him the ability to read the details of his surroundings, be it present or future. This makes the diary balanced but it won't tell him anything about himself which leaves him open to certain attacks. Also the future on his diary is based on his viewpoint, that means on what he believes is true. It reflects his personality as a reclusive bystander. It is a cellphone.
- The Yukiteru Diary (雪輝日記, Yukiteru Nikki?): Is the diary used by series's deuteragonist Yuno Gasai, it shows her entries related to Yuki on intervals of 10 minutes each. The diary will tell her everything about Yukiteru Amano, but nothing about herself unless it is related to Yuki, therefore when combined with Yuki's Random Diary, the two can make a fearsome combination that covers each other's weaknesses. This diary reflects her obssesive love for Yuki. It is a cellphone.
- The Murder Diary (殺人日記, Satsujin Nikki?): The diary used by The Third, Takao Hiyama. It gives him entries on who his next victims are going to be, and where they are. However it does not tell him what his victims will do, therefore he can't know which kind of attack will be used against him. It reflects him as a psychotic serial killer. It is a cellphone.
- The Criminal Investigation Diary (捜査日記, Sōsa Nikki?): The diary used by The Fourth, Keigo Kurusu. It gives him details of criminal activities done within 90 days, and will tell him only of his own investigation. It reflects him as chief of the police. It is a cellphone.
- The Hyper Vision Diary (はいぱーびじょんだいありー, Haipā Bijon Daiarī?): The diary used by The Fifth, Reisuke Houjou, it gives him 3 entries per day, for morning, noon and night. While it may seem weak, it allows him to plan his full day to attack 3 times a day, however if all of them fail, he must wait until the next day for more entries. His diary may reflect his rather impatient and childish behaviour since he's a kid. It is a colouring book.
- The Clairvoyance Diary (千里眼日記, Senrigan Nikki?): The diary used by The Sixth, Tsubaki Kasugano, it shows entries of what her subordinates see, this means that she can have many entries and strategically direct her men. However if they are tricked, it is likely that she does not know, even if she does she won't know what is true. It reflects her as the leader of the cult, and also how she cannot see by herself. It is a scroll.
- The Exchange Diaries (交換日記, Kōkan Nikki?): The diary used by The Seventh Duo, Marco Ikusaba and Ai Mikami. A pair of diaries that tell the future about each other, which allows them great teamwork as they can protect each other, the diaries are weakest when separated. It reflect the mutual love shared by the duo. It is a pair of cellphones.
- The Blog Diary (増殖日記, Zōshoku Nikki?, "Propagation Diary"): Also translated as the Server Diary, is the diary used by The Eighth, Kamado Ueshita, it allows her to create Apprentice Diary Users (see below). This means that while she can give anybody the power of a Future Diary, she can't read the future herself, therefore she needs somebody to fight on her stead. It reflects her loving nature as director of an orphanage. It is a laptop.
- The Escape Diary (逃亡日記, Tōbō Nikki?): The diary used by The Ninth, Minene Uryu, its entries reveal any escape route available to her, if any (where to go, how long to remain hidden, etc.). This means it won't tell her anything to attack her opponents. It reflects her nature as a survivalist since a young age. It is a cellphone.
- The Breeder Diary (飼育日記, Shiiku Nikki?): The diary used by The Tenth. Karyuudo Tsukishima, it allows him to control dogs and see the future of them (if they found somebody, etc.). The greater the number the more concentration needed to control the multiple dogs in teams. It reflects his great love for dogs. It is a cellphone.
- The Watcher (ザウォッチャ Za Otcha): The diary used by The Eleventh John Bacchus, it allows him to peep in the entries of the diaries, even those from Apprentices, which allows him to know exactly what will his enemies do, and how to catch them off-guard, even to plan countermeasures. Since it only reads others, however, he can't know the degree of truth of those entries, therefore he's vulnerable to misinformation and doesn't receive any Dead End flags. It reflects him as creator of the diaries. It is a tablet.
- The Justice Diary (正義日記, Seigi Nikki?): The diary used by the Twelfth, Yomotsu Hirasaka, it allows him to listen to his own righteous deeds that he will do in the future and it seemingly allows him to hypnotize people. It reflects him as the just vigilante he claims to be. It is a recording device.
- The Video Diary: (Game Only) The diary used by the Thirteenth, Azami Kirisaki, it allows her to visually record the future and shows her what she will record on her diary. It is a digital video camera.
Along with the Future Diaries is a special type known as the Apprentice Diaries. This diaries are specially provided by The Eighth's Blog Diary, as it has the power to make anybody (mostly users of electronic devices) a Diary Holder itself through connection to the server. Apprentice Holders are introduced at mid-way through the game mostly when both The Seventh and The Eighth make their moves as most of the Apprentices seen are in fact orphans under the care of Kamado Ueshita. After the appearance of these Holders, Deus himself tried to clarify some points regarding them and the game. Although he never clearly states anything about them some things are known as other are hinted, they are:
- The Apprentice Diaries also reflect their Holders, on particular traits. Although some Holders are not really given any background some examples are seen to follow this rule.
- If the Diaries are broken, the Holders do not die, possibly because this is an extra power provided by The Eighth, rather than by Deus himself.
- The Apprentice Diaries are vulnerable to jamming. If by any chance the connection between the diaries and The Blog Diary is interrupted, then the diaries lose their power. They are the only known type of diary vulnerable to jamming as the normal diaries are seemingly immune to this effect as seen during the attack against John Bacchus and The Seventh.
- It is an alleged suggestion that they cannot become God. The orphans themselves state they want to make Ueshita God, but this does not truly prove whether they can or not, although given that their condition is special rather than by Deus, it is believed that it is impossible for them to become God, nor has any Apprentice User ever attempted this.
- A regular participant can also use an Apprentice Diary.
- Apprentice Diary users can join with whatever party they see fit, not necessarily the Eighth's.
- Although never seen, it is suggested that once given, they cannot be taken back.
The following is a list of the known Apprentice Diaries and their users if known:
- The Flirting Diary: Used by Ai Mikami. It allows her to check with which men she's going to flirt with. Mostly used to track targets.
- The Brawler Diary: Used by Marco Ikusaba. It allows him to predict his opponents moves while brawling.
- The Orphan Diary: Used by Orin Miyashiro. Unknown, but suggested that it predicts the future of Ueshita's Orphans.
- The Copy Diary: Used by Ta-kun. By making connection with a diary, it is capable of copying its abilities, it can copy even normal Future Diaries.
- The Kosaka King Diary: Used by Ouji Kosaka. It predicts his successful moments, mostly used to reverse a situation. It does not tell him of his failures therefore he can fail if he relies too much on his successess.
- The Neo Kosaka King Diary: A replacement of the previous, this one predicts the successes of Kosaka and his friends. Suggested that it has the same weakness as the previous one.
- The Friendship Diary: Used by Hinata Hino. It predicts conversations she will have with friends.
- The Hinata Love Diary: Used by Mao Nonosaka. It predicts anything related to Hinata, working in a similar way like Yuno's Yukiteru Diary.
- The Secretary Diary: Used by Ryuji Kurosaki, John Bacchus' Secretary. Its entries are actions by John, serving as a shield whenever John's The Watcher is under misinformation.
- The Detective Diary: Used by Aru Akise. It can read the entries of the Diary Users and predict their future.
Deus at one point reveals that before the game was hosted, he and John created a few prototypes. As of the events in the series they are never used by anybody and were therefore scrapped, but have been named and detailed, they are as follows:
- The Radar: Predicts ones surroundings. A likely prototype version of Yuki's Random Diary.
- The Searcher: It predicts certain people's actions. A likely prototype version of Yuno's Yukiteru Diary.
- The Supplier: Can provide others with Diaries. A likely prototype version of Kamado's Blog Diary.
- The Organizer: Gives details about an organization. A likely prototype version of either Tsubaki's Clairvoyance Diary and also Karyuudo's Breeder Diary.
- The Watcher: Initially a prototype, it was decided that John would use it in the game.
Future Diary -Another:World-
In the Drama series, the diaries work mostly the same, save for few differences:
- The diaries are all cellphones provided by the Chronus Company. And possibly by Deus.
- All the diaries are equal in appearance.
- Dead End entries have two phases, the first one in which the entry appears in a red coloured background. The second phase starts so as long as nothing is done to prevent the Dead End and instead the future follows its normal course. When the Dead End's conditions start to be met, a countdown is shown next to the entry, revealing how long the Holder has before being killed. Deus reveals the only way to evade a Dead End is to kill someone else. It is said that if the countdown reaches 0 even if nobody does anything, the person will die, although this is unknown as any chance has been interrumpted by the death of another Holder.
- The diaries have different noises depending on the diary when entries appear, however the overwriting of an entry by defying the future is similar to that of the anime series.
The following is a list of the known diaries in the drama series:
- Arata's Diary (temptative name): Similar to Yukiteru Amano's Random Diary it seemingly predicts the surroundings of Arata, but say little to nothing about himself. They vary in time intervals and can predict things that will happen very soon to later events.
- A-kun's Diary: Similar to Yuno Gasai's Yukiteru Diary, it allows Yuno Furusaki to predict everything about Arata. It is hinted that it also gives details of his past, although it is unknown if this is due to the diary or plain stalking
- Megumi Fuwa's Diary (tempative name): Not much is known about her diary, except that it seemingly predicts things about herself and tell her about those she may or may not trust.
- Murder Plan Diary (temptative name): This Diary is used by the serial killer Yousuke Okuda and works almost like Takao Hiyama's Murder Diary. It allows him to calculate the success chance of a plan designed to kill his victims to choose the best course of action. Presumed to range from 0%-100% with the highest ever seen being a 87%. Even the "best" chances are so far not fail-safe as they have a margin of failure, and can even give him a Dead End with even a high success chance.
- Kinjiro Hagito's Diary (temptative name): This diary belongs to Kinjiro Hagito and works like Keigo Kurusu's Criminal Investigation Diary, predicting the crimes he will investigate.
- Tohru Kibe's Diary (temptative name): The diary belongs to Tohru Kibe and works like John Bacchus' Watcher Diary. The profiles of the other diary owners are also present on Kibe's laptop and computers.
- Haruna Okie's Diary (temptative name): The diary belongs to Haruna Okie. Her diary apparently did not start until halfway through the game, although she reveals this to be a lie. Her diary entries appear to be quite long and descriptive, although it is possible it predicts quite a lot in advance. Haruna's diary seems to focus a lot on Rui and Arata.
- Family Diary (temptative name): Used by Kurou Hoshino and works almost like Tsubaki Kasugano's Clairvoyance Diary. It predicts what happens to his son and wife. Revealed to be a lesser model of the Future Diaries made by Kibe.
- Deus' Diary (temptative name): The diary controls the virtual reality of Olympia and the user is allowed to be granted one wish with it.