Most Japanese schools do not employ janitors or custodians. The Japanese education system believes that requiring students to clean the school themselves teaches respect, responsibility, and emphasizes equality
They hire maintenance staff, but no janitors. This is because the students and staff do all of the cleaning themselves. This takes place every day, usually for 10 or 15 minutes, depending on the school, longer before vacations, and sometimes twice a day. (This might happen the day of the school festival, or on graduation day.)
It is considered a very important part of the hidden curriculum, a way to show gratitude to the school itself, a team-building exercise, and a part of learning how to be a grown-up.
Students typically sweep all the floors in the school, swab them with rags, bundle up papers amd carry them out, carry out trash, and clean the blackboards. Depending on the day, they might also do raking or shoveling.
The maintenance person assists with this process, in my school by managing the garbage station. For the rest of the day, he did necessary repairs and maintenance, such as changing light bulbs and mowing the grounds.