Sasaki

Sasaki behaves as a conventional teacher responsible for students at West High.

His appearances are too limited to establish an extensive private personality, family history or personal ambitions.

Like the overwhelming majority of the school's staff, he initially has no understanding of the creatures operating within human society.

Sasaki is an ordinary human without supernatural abilities.

His skills and authority are those of a schoolteacher rather than an investigator or combatant.

He cannot detect Parasite signals and has no means of recognizing a Parasite that successfully maintains a human appearance.

Sasaki appears among the faculty at West High while Shinichi Izumi is attempting to continue an ordinary school life.

His workplace is infiltrated by Ryouko Tamiya, who initially operates within the school under the appearance of a human teacher.

Sasaki remains a minor faculty member rather than becoming directly involved in Shinichi's secret conflict with the Parasites.

Shinichi Izumi is a student at West High, where Sasaki teaches.

Ryouko Tamiya works within the same school environment while concealing her nature as a Parasite.

Hideo Shimada later enters West High as a student, placing faculty members such as Sasaki unknowingly close to another Parasite.