The player character, working at 'The Sushi House', arrives for their first day. They are greeted by the head chef and introduced to their coworker, Yuki, who will be training them. The manager appears briefly, exhibiting a harsh demeanor. The player learns how to start their shift by mopping the floor and is then taught the intricate process of preparing sushi for customers, including understanding various plate types, sushi types, and the use of a conveyor belt system. They also learn about potential rail circuit breakdowns and how to fix them.

After their first shift, the player has dinner with Yuki. Yuki mentions the 'Manser virus', a terrifying disease that makes people crave human flesh, but victims appear normal. She alludes to a strange, hidden space within the restaurant and promises to tell the player more the next day. The player learns of the virus's airborne nature through shared dreams, causing concern about the sushi served in the restaurant.

On the second day, Yuki is called into the manager's office shortly after talking about the restaurant's secret. The player attempts to deliver a business card to the manager and overhears him harshly questioning Yuki about something she found. Later that night, Yuki shows up at the player's home, urging them to come back to the restaurant to witness the secret for themselves. They discover a hidden passage behind the locker room, leading to a gruesome basement where the manager is preparing 'meals for the infected', implying the sushi house serves human flesh.

The player wakes up with a sore neck, dismissing the previous night's events as a dream, but the lingering pain suggests otherwise. At work, the chef informs the player that Yuki is ill. The player notices a mark on their own neck, similar to a hickey, and hears a strange draft, further fueling their suspicion that the dream was real.

The player returns to the secret passage and is confronted by the manager, who reveals his sinister intentions and claims no one can leave. A terrifying chase ensues, leading the player to their apartment, where a detective from Major Crimes is waiting. The detective informs the player that Yuki is missing and asks about unusual occurrences at the sushi house. The player recounts finding the hidden passage and the manager's threats. Yuki then calls, claiming to be trapped underground and explicitly warning against involving the police. The player chooses to call the detective anyways and then heads to the sushi house.

The player infiltrates the restaurant's basement, avoiding the manager, to find Yuki. They discover a confidential report revealing the 'Manser virus' is transmitted through shared dreams and connected to a 'reverse domain'—a mirrored reality. Those who pass through this domain become 'perfect hosts' for the virus. The player is ultimately ambushed by the manager and forcefully turned into a 'perfect host', implying a bad ending where the player succumbs to the virus and becomes a cannibal.

In an alternate outcome, the player chooses not to call the detective and instead trusts Yuki. Yuki reveals that the detective is also infected and working with the manager. Together, they plan an escape: either finding a key to the secret passage or using the ventilation system. They manage to distract the manager and escape through the ventilation system. They then contact the police, leading to the manager's arrest and the uncovering of the human flesh operation at the sushi house. Both the player and Yuki survive, though they acknowledge that the fight against the Manser virus is far from over, and its influence on society continues.