Japanese supervisor does not respond to my emails

Hello all,

I am a permanent researcher working at a national institute in Japan. When I email one of my direct supervisors (It is Japan, there are many supervisors…) to ask for information, he never replies to me. He does not seem to be particularly busy.

My emails are written in correct and polite Japanese, following the appropriate rules of hierarchy and position.

At first, I did not think much of it, but after several occurrences, I started to wonder why this keeps happening.

I asked my Japanese colleagues whether they experience the same issue, and they were quite surprised. According to them, he always replies to their emails.

This made me wonder whether this could be related to the fact that I am a foreigner.

However, when I meet this supervisor in person, our interactions are normal, and he is usually friendly and polite.

What do you think about this situation? Have you encountered similar cases?

For context, I consider myself a very normal and professional person. I have never caused any trouble that could reasonably explain this kind of behavior toward me.

Edit 1) I confronted him once, he just said "sorry".

Edit 2) sometimes email is required when sharing some files etc.

Edit 3): researchers are often not at their office (fieldwork, meetings, telework)

Edit 4): even if I email a second time. No difference.

Edit 5) I am not Complaining, just asking for opinion and suggestions, or info on similar cases.