Human Vapor

A mysterious gaseous entity enters a professor, Sano, causing him to explode on live television, leaving the public in terror. Detective Kenji Okamoto and reporter Kyoko Kono are independently assigned to investigate his death. They are ex-lovers, and Kenji is still bitter that Kyoko failed to appear at his engagement proposal and broke up with him. He was also suspended from the police force after Kyoko aired a special investigative report on Yasutoshi Mori, an ex-Yakuza turned businessman, who was suspected of killing a teenage girl by making her overdose on drugs, which led to his "suicide"; his superiors believe his negligence allowed her access to the files.

Later, a mysterious man who can transform into a gaseous form takes credit for the murder and calls himself "the Human Vapor". During an interview with Kyoko and her news crew in an abandoned restaurant, Bunko Ramen, the Human Vapor vows to kill everyone involved with something called "the White Center", later escaping after Kenji and SWAT police fail to capture him alive.

Kyoko and her crew learns that the White Center used homeless people and orphans for forced labor under the guise of being a welfare facility. The White Center was involved with the cleanup of a meteorite crash site 27 years ago and the murdered professor was the head of the safety committee which covered up the toxic nature of the site. Kyoko tracks down the former director of the White Center, Hiroki Obata, and convinces him to agree to hand over his journal detailing what transpired. While looking through the journal, Obata realizes that the Human Vapor was a cleanup crew member who was listed as missing. Meanwhile, Kenji discovers a clue that a yakuza gang might be the next target. The Yakuza send an assassin that kills Obata and steals the journal before he can give it to Kyoko.

The Yakuza obtain a video recording of the journal's contents from their assassin and use it to blackmail another involved party known as "Mufu". The assassin burns the journal and is then murdered by Kenji's corrupt coworker, Inspector Yoshida, who is a double agent working for both the Yakuza and Mufu. Kenji prepares a police raid on the Yakuza stronghold, while Kyoko and her news team surveil them. The Human Vapor "accidentally" appears at night just before the police raid, make chaos and chases the yakuza boss, Otomo, through the streets. After the Human Vapor kills him, Kyoko arrives at the scene, stealing Otomo's phone and sending the video recording to herself before the police arrive.

Siblings Fujita and Kaho Fujikawa run an unsuccessful livestreaming channel called "The Terror Zone". They discover a clue to the Human Vapor's origins in the background of an old underground idol group's music video. A viewer of their stream, "dadashow", offers to buy the information off them for ¥1 million. Spurred by the offer, they investigate further and discover the resting place of the Human Vapor in the basement of an abandoned workshop. They find the Human Vapor as a frozen statue that comes to life upon hearing a specific song recording and learn that "dadashow" is actually Kyoko.

Kyoko reveals to the siblings that she was an orphan at the White Center when the meteor cleanup occurred. She inadvertently escaped the White Center after discovering the dead bodies of the cleanup crew. She controls the Human Vapor, remotely giving him targets to kill. However, she does not understand the full conspiracy; her investigation served to identify other members of Mufu. She lets the siblings go, urging them to only go public after she has taken her revenge. Kaho abhors the murders, while Fujita, desperate to become successful and lift them out of poverty, sneaks back to the Human Vapor and uses him to film another message, this time threatening the Superintendent General Mamoru Sakamoto of the Tokyo Metropolitan Police with death if he does not admit to his crimes.

Kyoko and Kenji visit Sakamoto, who was listed in the journal. He claims that the actions of the White Center were for the greater good, saving many more lives than were killed by the meteorite cleanup. His guilt leads him to organize a press conference, to give up the last member of the conspiracy, only known as Kai, and everything else he knows. He also claims he was responsible for the death of Kenji's father, but refuses to elaborate. Before he can go into public, corrupt Inspector Yoshida, who still working for Mufu, kills him and stages it to look like suicide in his private car. He then sends the Yakuza to the Fujikawa siblings as Fujita's video goes viral.

A flashback shows how Ren Tsutsumida, the man who became the Human Vapor, was one of many victims forced by the White Institute to attempt to destroy the meteorite. He successfully plants explosives that bury the meteorite, but in the process, he is exposed to enough of its anomalous energy to become the Human Vapor, later vanishing for years.

The Yakuza abduct both of the Fujikawa siblings in order to find out how they received the Human Vapor message.

Kyoko reveals the connection between Sakamoto, the Center, and Mufu to his widow. She reveals that Mufu is actually the name of a band that Sakamoto started in high school, with Otomo (the Yakuza boss) and the mysterious Kai, who is actually politician Takeshi Miura, one of the candidates running for governor of Tokyo. Despairing, she sends the order to the Human Vapor, but his awakening is interrupted by the Yakuza, working for Miura.

Miura has learned how to control the Human Vapor after torturing Fujita, and orders him to kill the siblings as they flee. Fujita sacrifices himself, dousing himself in gasoline before setting himself alight as the Human Vapor enters him, allowing Kaho to escape.

Kenji investigates his father's belongings and finds that he was investigating the White Center before he died in an accident. He then searches through police records and finds that Otomo's lieutenant Mori was arrested for an assault at Bunko Ramen, the same restaurant the Human Vapor chose to be interviewed in. A polaroid on the wall reveals Ren with a young Kyoko. She confesses to Kenji, but they instead go on the run as the Tokyo Metropolitan Police put out a warrant for her arrest.

Governor Miura calls an emergency press conference, labelling Kyoko as the Human Vapor's accomplice. He plans to use the Human Vapor to sow terror, so that voters will choose his promises of stability over his challenger.

Kyoko reveals to Kenji that after her escape from the Center, Ren adopted her. At Bunko Ramen, Kyoko's mother and her boyfriend Mori assaulted Ren and attempted to use their White Center connections with the police to take Kyoko back. Kenji's father stopped them, so they made a deal with Ren: do one job, and they will stop pursuing Kyoko. The job in question turned out to be the meteorite cleanup, and Kyoko witnessed Ren's transformation and apparent death.

Six years before the present, Kyoko, as a junior reporter, returned to Ren's workshop and founded the Human Vapor in the basement. Trying to awaken him, she discovered that the recording of Ellie My Love, their favorite song, returned him to human form, but he could not respond and simply asked what wish he could fulfill. After seeing the files on Mori's continued abuses, she attempted to provoke a confession through an ambush interview. When Mori expressed no remorse, Kyoko wished for the Human Vapor to kill him, making it look like a suicide. Mori gave up Otomo and Professor Sano, starting Kyoko's revenge, while Mori's apparent suicide led to Kenji's suspension.

Kaho manages to contact Kyoko, but before they can meet, she sees the Human Vapor in the crowd. It ignores her, and she follows it to a campaign office for Miura, which explodes in a false-flag attack.

It is revealed that Miura was inside the office, but survived. Kyoko, Kaho, and Kenji escape but are uncertain as to who ordered the new attack by the Human Vapor. They return to Ren's workshop to retrieve a camera Fujita left to record the Vapor, and confirm that Miura ordered it to kill his election staff and a large number of homeless people, but to leave him alive. They realize it is all a ploy to secure his re-election. Kenji is beaten and taken by the Yakuza, while Kyoko and Kaho escape with the recording.

Miura tortures and threatens him, and discovers that Kyoko has the recording and will air it. Miura wishes for the Human Vapor to kill Kyoko and destroy the recording, but this was Kyoko's plan all along. Kenji manages to fight back the Yakuza and escape, Kaho posts a copy of the video to her channel (recreating her brother's occult presentation style) and Kyoko sends a copy of Obata's journal to her colleagues at the news network. The video goes viral, and public support immediately turns against Miura.

Kenji goes back to the police precinct, convincing many of his colleagues to join him in arresting Miura, and is nearly assassinated by the corrupt cop Yoshida, who is stopped by his partner and accidentally bisects himself on his own piano wire, leads his brutal death. Miura flees to the roof of his campaign office, shooting and wounding several officers before attempting suicide. He nearly takes Kenji with him, but his fellow officers pull both of them back up to the roof.

Meanwhile, Kyoko leads the Human Vapor to an airtight, blastproof vault below the old NFT news network building. As Kenji arrives, he sees a wounded Kyoko being billowed up by the Vapor before a human face forms in it and they both disappear in a flash of light.

A year later, the truth behind the White Center and Ren and Kyoko's origins has been made public. Kyoko and Kenji's partners meet as part of a news special, paralleling Kyoko and Kenji's first meeting. Kaho is now a successful streamer, fulfilling her late brother's dream. Kenji visits Kyoko's grave, before returning his home. As he puts on Ellie My Love and falls asleep, a vapor coalesces through his window and a female form appears behind him, leaving Kenji's reaction unknown.