The character known as Dry Cleaner, or more simply the school cleaner, is a minor but memorable figure in Prison School. He works as a janitor and laundry attendant at Hachimitsu Academy, specifically responsible for running the launderette attached to the girls' dormitory where boarding students submit their uniforms and other clothing for cleaning. He is employed by an outside contractor rather than directly by the school itself.

In terms of appearance, the Dry Cleaner is a bald, heavyset adult man with a short beard. He is consistently shown wearing an apron over a collared shirt and trousers while working, or a white shirt and jeans when off duty. Notably, dark shadows perpetually obscure the area around his eyes, making his eye color and exact expression difficult to discern.

His personality is marked by a sense of pride and a quick temper. He is easily provoked, as demonstrated when he becomes enraged by Gakuto’s verbal insults. However, beneath this gruff exterior, he is not entirely unkind, as he is capable of befriending students like Shingo and is willing to offer help when the situation calls for it. His primary motivation appears to be the competent execution of his duties, which include collecting dirty laundry from the girls' dorm basement every Friday afternoon. He is shown to take his work seriously and reacts with anger when his routine is disrupted, such as when Kiyoshi leaves a laundry basket in the path of his pickup truck.

His role in the story is functional, serving as an obstacle and an accidental aid to the main characters. He becomes directly involved in Kiyoshi’s desperate plan to sneak a girl’s uniform from the laundry to meet Chiyo. Kiyoshi hides inside the cleaner’s pickup truck while Gakuto distracts him with insults. The cleaner takes the bait, angrily confronting Gakuto until Shingo steps in to apologize, inadvertently befriending him in the process. Later, the cleaner remembers Shingo from this incident and helps him by giving him a ride back to school in an attempt to get him there before curfew, shouting encouragement for him to run. Despite this assistance, Shingo ultimately fails to return on time due to other circumstances.

Key relationships include a brief but impactful positive connection with Shingo, who calmed his anger and earned his respect. His interactions with Gakuto and Kiyoshi are antagonistic, as they directly scheme against him for their own purposes. The character undergoes minimal development, remaining a static figure whose primary narrative purpose is to facilitate a single major plot point. He possesses no special abilities beyond his role as a driver and laundry worker, though his familiarity with the school’s cleaning routes and schedule is central to the storyline involving Kiyoshi’s jailbreak. As a minor character, his appearances are limited, and his real name is never revealed.