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Takao Hiyama (火山 高夫 Hiyama Takao) is the Third diary owner. Ostensibly the homeroom teacher of Yukiteru Amano and Yuno Gasai, Hiyama moonlights as a serial killer, hunting down women and killing them with a large knife or machete. He owns the "Murder Diary" (sometimes called the "Killer Diary" in the manga).


Little of Hiyama's personality is revealed during his short time in the story, but as a teacher he enjoys dropping surprise math tests on his students, and is shown to be a bit strict, however he could be seen as friendly at times, and this was shown in the scene where he allows Yuno to make her clay model of Muru Muru, though it only may be because of the reason that she claimed it was a brain exercise.

It seems as if his true self is a manipulative sadist, when he was shown to warn his class to be aware about the serial killer, even though the serial killer was revealed to be Hiyama himself. Hiyama is also shown to be very paranoid, as he was known to destroy his Future Diary twice when Muru Muru first introduced it to him, yet he still believed that she was recording his crime on the diary, and again under the belief it is evidence. Muru Muru also predicted that he would be the first Diary holder to die due to his paranoid nature and it was shown to be correct.

Diary & Abilities

Hiyama's Future Diary is the "Murder Diary", which predicts how and where he will kill his next victim, and how best to corner and kill them. This also works when he identifies several of the diary owners, allowing him easily track them down. However, his diary has weaknesses, namely if his victim contradicts the entries on his diary (namely fighting back) then it is rendered useless.

As the serial killer he is, Hiyama wears a hat, gas mask with googles and a bulletproof and apparently explosive proof jacket. This makes him impervious to almost anything except few things; Minene Uryu had to defeat him by luring and trapping him in a room and set of an explosive, severely stunning him with the noise. His trademark weapon is a large machete-like knife.

Despite of this he does have many weaknesses, his paranoid demeanour along with the fact he merely corners his victims and stab-slice them with his knife.

With such a simple fighting method, Hiyama is not really as smart or cunning as many of the other diary users, and his own diary only shows him how to corner his victims but not how to defend against them, which has been exploited several times across the series.

Overall, this makes him the weakest of the participants, which Muru Muru reinforces by believing he would be the first participant to be eliminated from the Survival Game.

Future Diary: Paradox

In this alternate addendum to the manga, Muru Muru accidentally kills Yuno Gasai.  This seemingly trivial incident actually has a severe aftermath. Without Yuno to protect Yuki, Hiyama manages to corner him and comes very close to killling his student.  After stabbing him in the chest wth his trademark knife, Hiyama moves to destroy Yuki's Diary, but is interrupted by the timely arrival of Akise Aru, who is taking Yuki's place in the Survival Game.

After a brief scuffle, Hiyama attempts to stab Akise as well, but narrowly misses, and his blade embeds itself into a circuit box, which ends up electrocuting him to death.



  • Hiyama is named after Vulcan, the Roman god of fire and craftsmen. Interestingly, his surname means "volcano".
  • Hiyama's character theme song is "THIRD/Antares Cr302" by Aki Hata.
  • While wearing his serial killer outfit, Hiyama bears a striking resemblance to Ben Willis