Chaos;Head is a visual novel game in which the player takes the role of Takumi Nishijou,[1][2] an otaku and shut-in, who experiences delusions.

Positive delusions generally involve comical or erotic scenes, while negative ones include horror elements and violence.

The game is set in 2009 in the Shibuya district of Tokyo, where Takumi lives in a cargo crate on top of an apartment building.

[1] He discusses the recent "New Generation Madness" ("New Gen") serial murder case in Shibuya with his friend Grim over the internet, when someone with the username "Shogun" sends Takumi image files depicting a man pinned to a wall with stakes.

As he becomes a suspect and more murders occur, Takumi worries that Shogun is targeting him and experiences paranoia and hallucinations, and becomes unsure of what is real and who he can trust.

His sister Nanami is held in the location of the real Noah II, where she is made to awaken as a Gigalomaniac and obtain a DI-sword.

Takumi obtains a DI-sword, and destroys the transmitters, revealing the nurse Hazuki to be the New Gen killer in the process by reading her memories and projecting them onto the screens on the buildings.

[4] It was planned by Chiyomaru Shikura,[5] the founder and executive director of 5pb.,[3] and was written by Naotaka Hayashi, with character designs by Mutsumi Sasaki and concept art by Yukihiro Matsuo.

[7] Chaos;Head was originally announced under the title Gigalomaniacs (ギガロマニアックス, Gigaromaniakkusu),[8] and was released for Microsoft Windows on April 25, 2008, by Nitroplus.

[4] Around June 2008, the developers decided to port the game to Xbox 360 with added content:[9] this version was released on February 26, 2009, as Chaos;Head Noah.

[19] An English localization of Chaos; Double Pack by Spike Chunsoft was eventually announced in March 2022, and was released on October 7, 2022.

[21] However, edits found within Steam Database in August 2022 led to rumors about Chaos;Head being preemptively banned from the platform.

[32] Writing for Kotaku, Richard Eisenbeis found Takumi very unlikable, to the point of being unsure whether the player is meant to sympathize with him.

Complaints included questionable typography choices such as the lack of quotation marks to indicate dialogue, mistranslations that distort the meaning of certain moments, writing that fails to capture the personalities of the characters, and CGs that were untranslated from the original Japanese and instead had subtitles overlayed onto them.

Additionally, the TIPS menu was also criticized for including translator notes and explanations, which was considered to be at odds with its original purpose of providing a glossary for slang and jargon used within the story.

[37] A manga adaptation by Sumihey started serialization in ASCII Media Works' shōnen magazine Dengeki Daioh on May 21, 2008.

[38] A second manga, Sakaki Nagako's Chaos;Head: Blue Complex, adapting the events of the story from the character Sena Aoi's perspective, began serialization in Media Factory's seinen magazine Monthly Comic Alive on September 27, 2008.

[39][40] A romantic comedy manga adaptation, Mizuki Takehito's Chaos;Head H,[b] was serialized by Jive in Comic Rush beginning on September 26, 2008.