Keisuke Muroto is a freelance journalist who previously attended the same school as the protagonist, Tsutomu Senkawa, and continues to maintain ties with the campus due to his connection to the journalism club. His professional work is driven by an intense curiosity for unexplained phenomena, with a particular focus on investigating supernatural occurrences and seeking evidence of alien existence. This motivation leads him to closely follow two figures he believes hold significant secrets: the popular idol Shion Arita and the influential businessman Satyajit Shyamalan. Muroto possesses sharp instincts for uncovering stories and often rushes to the sites of unusual incidents to conduct immediate research, though his impulsive and headstrong approach frequently places him in dangerous situations.

In the story, Muroto is first drawn into the central conflict when he attempts to photograph the alien criminal Bacillus and the Federation officer Birdy during a movie shoot, only to be knocked unconscious by falling debris. His role as an investigator proves more significant as the series progresses. Alongside journalism club chairperson Natsumi Hayamiya, he investigates the aftermath of the Ryunka explosions in Sawajiri Village, where his pursuit of the truth leads to a lethal confrontation with armed men under Shyamalan's command. This event demonstrates his willingness to risk personal safety for a story. His professional rapport with Hayamiya is notable; he recognizes her similar investigative drive and treats her as something of a protege. Muroto also develops a connection with Tsutomu Senkawa, as their shared school background and Muroto's investigative interests naturally draw them together. In the climactic events, Muroto makes the active decision to help Tsutomu after discovering the location of the Lost Bird, the ship where Sayaka Nakasugi is being held, showing that his commitment extends beyond mere journalism to genuine concern for others.

Keisuke Muroto is physically characterized by his dark brown hair and black eyes. While he does not possess any supernatural powers or combat abilities like the series' alien characters, his primary asset is his investigative skill and persistence. His notable abilities include a keen eye for detail, sharp instincts for identifying stories of importance, and the courage to pursue dangerous leads despite the risks. Over the course of the narrative, he is described as ultimately revealing himself to be a supportive individual beneath his ambitious exterior, moving from a peripheral observer to an active participant in the events surrounding the Ryunka crisis.