In America we have "Indoor Voices," in Japan we have

Indoor shoes.
Japanese slippers are called uwabaki. These are indoor shoes and are often made of a light, flexible material with rubber soles.

In Japan, you must take off your shoes upon entering a house and often don on a set of these. This same rule applies to some restaurants, work places, and schools. All of my students have a regulation slipper that they all wear inside the school. Additionally there is a different slipper, located at the bathroom slipper entrance,  to be used when going to the bathroom. This practice is also popular in restaurants and homes. By having special slippers for only bathroom use, contaminants that might be on the bathroom floor are kept out of the rest of the establishment or home. This practice is also upheld in Korean schools and residences and, from personal experience, is also much more common to see in Korean restaurants as well.

these are my home slippers

At the schools, there are individual lockers for everyone's shoes. These lockers will occasionally have a dividing shelf to separate the indoor from outdoor shoes. In addition to indoor, outdoor, and bathroom shoes, my students also have indoor gym shoes. This helps stop the floor from being marred by outside elements and maintain its polish for longer.

the shoe boxes,
seen upon entrance to the school grounds.

every student has their own shoe box.
it is separated by grade level and classes

school slippers

On a side note. I severely dislike the uwabaki provided for me by the schools. There is a small lip to them on the front and I am constantly tripping on the stairs. Additionally there is no back to them so they function more like clogs; essentially, I am dragging my feet around all day. Anyone in the building can hear me coming from a few floors away thanks to the shhhhp shhhhp shhhhp of my slippers dragging on the groung, unable to lift my feet off the cement lest my slippers fall off!
Luckily, it is perfectly acceptable and often encouraged to bring your own shoes for work, which for many of the teachers here is sneakers or Crocs.

As far as I can tell, the reason for wearing uwabaki is a way of maintaining a cleanly interior to minimize said cleaning. It is also efficient in minimalizing the introduction of bacteria around the home, specifically the bathroom.