"It was a human." is a short SF psychedelic interrogation adventure game that focuses on the interrogation of a suspect in a dismemberment murder case.

The game's setting begins with a murder that occurred in a hotel in Kase City, Saga Prefecture. When the police arrived, they discovered the bodies of two unidentified men. The cause of death for each was presumed to be traumatic shock due to blunt force trauma and asphyxiation, respectively. Also, at the scene, a woman suspected to be the perpetrator, Okoze Isana, was found standing with a coping saw in hand. The investigation team considers her to be the murderer in the dismemberment case.

The protagonist of this game is a lieutenant colonel in the military, tasked with interrogating the suspect, Okoze Isana. The protagonist needs to find out why she killed the two men and how she committed the crime.

Okoze Isana might use sweet words or flirtatious glances towards the protagonist during the interrogation, but she is considered a villain and virtually a criminal. The condemnation of her is the objective of this game.