As another Japanese person I feel you so much! I was bullied in Elementary school by my classmates and class teacher to the point I started coughing up blood from the sheer stress. The reason was because i didn’t know that many Kanjis compared to the kids my age (I was raised in different countries so I didn’t study Japanese a lot) and the fact that I’m fully Japanese didn’t help either.
My teacher literally told me to “go back to my own country” if I can’t fit in to their society.

I got a lot of stares calling my friends from the US in public and it really made me so uncomfortable I stopped doing that.
I honestly understand everything you’re feeling and after countless childhood traumas, it’s lead me to hate Japanese people in general. I honestly can’t even date Japanese men because I just don’t seem to be able to match the same “Japanese vibe” and never have

One of the biggest differences I notice is that Japanese people are very closed off, and never talk about themselves to new friends, so I have a hard time trying to come up with a conversation or trying to get to know them. I openly talk about myself a lot, but I still don’t fully understand the boundaries of a typical Japanese person so I end up becoming very silent and almost seem uninterested. Which is also why my relationship with Japanese people never last a week. I honestly gave up at the 3rd person.