Mushiba-chan's job is "making cavities for people who don't brush their teeth." She is still an apprentice.
But she doesn't much like this work. It's her job, so she makes cavities because she has to.
At night the telephone rings, shrill and loud: a summons to work. She has to go on duty inside the mouth of someone who hasn't brushed, and report on "teeth that have gone a while without brushing." Report to whom? To the Supervisor at the Ministry of Cavities. When the check is done, the next morning she must go to the Ministry and file her report.
Mushiba-chan is a kind child at heart, so she keeps her reports as modest as she can. Nobody wants to see anyone in pain from a cavity, after all, and she would rather cavities didn't happen at all.
At the Ministry, a different cavity officer checks that the report has been properly filed, and then places an order with a specialist contractor for cavity works.
The works crew are craftsmen, and strict ones. Whatever they are asked to do, they do exactly, no more and no less. Just before the works begin, Mushiba-chan slips out in the middle of the night to look at the site. Maybe, just maybe, the person has started brushing, and this time no works will be needed. But almost always the teeth are still unbrushed. Mushiba-chan's shoulders sag, every time.
When the works begin, grrr-grrr-grrr-grrr, Mushiba-chan's tears come spilling down.
That is why you are still an apprentice, the Supervisor scolds her. Mushiba-chan thinks. If everyone brushed their teeth, and there wasn't a single cavity in any tooth anywhere... then she could lie down on clean white teeth, and that telephone would never ring, and she could take a long, long holiday... And then, surely, she could go somewhere far away. Those are the things Mushiba-chan finds herself dreaming of.
The end