Ajin Wiki
Yū Tosaki
Name Yū Tosaki
Kanji 戸崎 優
Rōmaji Tosaki Yū
Status Deceased
Age 25+
Gender Male
Hair Color White
Eye Color Blue
Occupations Head of Ajin Research
Height 182cm
Voice Actor Takahiro Sakurai (Japanese)
Todd Haberkorn (English)
First Appearance Chapter 1 (Manga)
Ajin Part 1: Shōdō (Film)
Episode 1 (TV Anime)
Image Gallery

Yū Tosaki (i戸崎 優, Tosaki Yū) is a high-ranked member of the Ministry of Health, Labor and Welfare.


Tosaki is an adult male that appears relatively tall. He has pale hair and dark eyebrows. He wears a white suit accented with black pockets, a pinstriped shirt, black gloves, and a pale gray tie. Also notable are his glasses, which have crooked dents in the arms, presumably so that he may have more ease looking out of his peripheral vision. On the left side of his chin, Tosaki has a dark mole.


Generally, Tosaki has a commanding air about him and wears a serious expression. His answers are always short and to the point. He is also quite blunt and lacks patience.

He's quick to anger with certain triggers, such as multiple instances in which he snaps at the mispronunciation of his name - "Tozaki" as opposed to what he claims is correct, "Tosaki".

From the very start, Tosaki is shown to be morally ambiguous. It isn't above him to resort to violence through either his own force or those beneath him to get something done. If the consequences of his actions don't have a direct effect on him, his reaction is mild at best.

Tosaki relies heavily on Izumi Shimomura to protect him from the Ajin (Race) and their IBM with her own abilities, threatening her with the prospect of being locked up and experimented on if he dies.


Tosaki's comatose fiance (Ai) motivates him to pursue the Ajin throughout the story and keep his job as the head of Ajin research at the ministry of health, labor and welfare. By extension he can pay his fiancee's hospital bills.



Ai is Tosaki's comatose fiancée. It is shown that her condition has greatly influenced Tosaki, becoming even more stoic and not opening to anyone. This could hint that they had a quite close relationship. Working at the Ministry of Health, Labor and Welfare has allowed him to pay her toll for the hospital.

In one of the chapters there was a flashback of their relationship before everything happened, with Ai telling Tosaki to stop smoking. He has regarded this later on as he takes mints with him instead of smoking. Tosaki seemed to really care for her.

Izumi Shimomura[]

Izumi is his bodyguard. He relies on her heavily, however, he does not hesitate to threaten her if she fails to do her job correctly. Even though it was shown that Izumi seems to understand Tosaki, she is still quite anxious in case of making a mistake in front of him, such as the time where she accidentally asked Kei's sister if her brother has seen as Black Ghost, later saying that she was glad that Tosaki wasn't there at the time. We discover that the reason that Tosaki still keeps Izumi's status as an Ajin a secret is because he considers her as a valuable asset in case anything might happen to him.

Kei Nagai[]

Their relationship is quite ironic, as they are technically on opposing sides (with Kei being an Ajin and Yū a human) but decided to work with each other notwithstanding. Kei only did it as opposing Satō would only put himself into danger, and he needed a strong ally. Tosaki was reluctant at first, but eventually agreed as it was the most logical thing to do. On casual occasions, Kei and Yū bicker around with a lot of sarcastic comments. Tosaki also forces Nagai to train vigorously, which Nagai hates. Ironically, though, their personalities are not so different as it may seem as they are both very cold and analytical. However, Kei considers Tosaki's love for his comatose fiancée a weakness and something that he can use against him.


  • The kanji in the surname Tosaki mean "door" (戸) and "promontory" (崎). Notably, "Tozaki" has the same kanji and meaning.
  • Pre-story, Tosaki smoked cigarettes. He appears to use mints as a tool to help him quit as per his now-comatose fiance's implication that she wanted him to stop so he would live longer.
  • Tosaki knows how to handle a tranquilizer gun as well as larger, lethal guns.