The origin of “Don’t forget to take off your shoes!”
“This traditional Japanese room has tatami floors. Don’t forget to take off your shoes!”
From Nintendogs + Cats 3DS (all versions)
We all walk in our socked feet (or slippers) all the time while indoors (in the case of the bathrooms in Japan, toilet slippers), as you’ve seen many characters (in both ancient and modern times) wearing slippers, uwabaki, or in socked feet in many anime and manga while they are at home, in elementary school (小学校 shōgakkō), junior high school (中学校 chūgakkō), or high school (高等学校 kōtōgakkō). Elementary, junior and high school students in Japan wear uwabaki and not normal shoes, in addition to wearing school uniforms¹ in Japan.
Just watch the video (by Japan Online):
Genkan (玄関) are traditional Japanese entryway areas for a house, apartment, or building — something of a combination of a porch and a doormat. It is usually located inside the building directly in front of the door. The primary function of genkan is for the removal of shoes before entering the main part of the house or building.
After removing shoes, one must avoid stepping on the tiled or concrete genkan floor (三和土 tataki) in socks or with bare feet, to avoid bringing dirt into the house. Once inside, generally one will change into uwabaki (上履き)²: slippers or shoes intended for indoor wear. Schools and public baths (銭湯 sentō) have large shoe cupboards (下駄箱 getabako) with compartments for each person’s outdoor shoes. In private residences, getabako may be absent, and shoes are usually turned to face the door so they can be slipped on easily when leaving.
Genkan are also occasionally found in other buildings in Japan, especially in old-fashioned businesses.
The real reason is walking in socks or bare feet while removing shoes when there’s a genkan does not mean foot fetishism. The tradition of removing shoes in Japan literally keep the floors clean. Japanese school children and high school students (pictures below) clean the classroom in their schools daily, as there are no school janitors in Japan (but have maintenance staff).
Cleaning-wise, 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 and carry them out, carry out trash, and clean the blackboards. They might also do raking or shoveling, depending on the day. We do have school and college janitors in the US and Canada which does all the cleaning.
There’s always a genkan in Japan, but a lot of households outside of Japan want to have a shoes off policy. The reason why I moved YouTube channels because there are foot fetish nerfheders on YouTube subscribed to my channel, as one of the videos are tying shoelaces (below).
They need to know that the new channel is an art channel, not a place for giving episodes of TV shows or anime due to avoiding copyright strikes on YouTube.
Genkan-wise, just wearing socks is also acceptable in informal situations. Socks are not generally removed — bare feet are acceptable when visiting a close friend, but not otherwise. There’s also tatami mats where they must be in socked feet or barefoot.
 I’m not going to put all the characters in my works in their school uniforms, but there will be supporting characters or other people wearing school uniforms.
 I’m going to put all the characters in my works wearing house slippers or just socks when they are at their homes or in temples.