Does this in any way count as cultural appropriation (and maybe racism) or am I overthinking this?

I wouldn’t call it cultural appropriation, nor racism, but I would question what you are thinking?

What are your thoughts about those names – what do they mean to you?

Why did you choose them for this character? Just for the way they sound? Anything else?

Why do you think this character would use these words? Where would they have heard them? What is the character’s cultural background and exposure to languages and these terms growing up? Is there some reason why they would have heard those forms of address, and why they would have chosen them?

If you have or can come up with solid satisfying reasons that make sense to answer the questions in the paragraph above, then you may have a reasonable explanation that may work.

If you’re not thinking anything about it except you like the sounds, and you know the character is Japanese and those names are not Japanese, then while it might not be racist, it would seem to be thoughtless.

What is an OC?

@elbanditoroso
“Original Character”, meaning a character he invented himself, and is not present in any source material.

Also, a Japanese character would not use “mami” or “papi”.
https://teamjapanese.com/mother-in-japanese/
https://teamjapanese.com/father-in-japanese/

If they are going to use english loan words, it would be “mama” and “papa”.

You are too into the color of people’s skin. Be color blind and you will see all people as equals.

No, that’s fine. Cultures can’t own words, they’re public domain. Use any word you want any time you want. If you live in the United States of America, see 1st Amendment for details.