In Japan, the more honored seat offered to a guest or someone senior to you is called the kamiza. The less honored seats are called shimoza, and they are often closer to the entrance. The exact position of the kamiza depends on the room, but in a traditional tatami room with a tokonoma alcove, the seat nearest the tokonoma is the most important clue.
There is also a general sense that the farther a seat is from the entrance, the higher its status. But when a tokonoma is present, distance from the doorway is not the only rule. If the seat farthest from the entrance and the seat nearest the tokonoma are not the same, the tokonoma side is usually treated as the kamiza.
The tokonoma is a special part of a traditional room, typically used to display a hanging scroll, flowers, or other seasonal decoration. Because of that status, the seat closest to it is traditionally offered to a guest or someone senior. If you are the host, it feels more natural to guide the person there with a simple “Please, sit here,” rather than leave them to work out the seating order themselves.
Most Japanese people are not mentally calculating the entrance and tokonoma every time they enter a tatami room. Many may barely think about kamiza and shimoza in ordinary life. But when a senior person is present, sitting down first in the most honored spot can still feel slightly wrong.
If a Japanese person does it without thinking, the reaction may go beyond “They don’t know the seating rule.” It can also come across as a little rude. Not knowing the custom and appearing impolite are not always separate things.
Foreign visitors are usually given much more leeway. If someone from overseas sits in the kamiza without realizing it, people are more likely to assume they simply did not know the convention. The same behavior from a Japanese adult may be judged more strictly.
These seating rules are not enforced as rigidly in every modern setting as they once were. Even so, knowing where to seat a senior guest is still considered basic professional etiquette.