Former (?) Japanese looking for options to move to Japan

Hello Reddit,

I am looking for the best/easiest way to move to Japan for my specific circumstances. Although I have done my own research, I have no idea how to get concrete answers specific to my case so I wanted more input on what I should do. Here are the context:

I was born in Japan with Japanese father and Vietnamese mother. My parents divorced and I went with my mother to US because she had no legal means to stay in Japan.

I had a Japanese passport and Japanese citizenship but had to get USA citizenship at around 18 because I was no longer going to be eligible as a dependent to my mother.

I was told by my mother that I will have to choose between revoking my Japanese citizenship to stay in America or revoking American citizenship to keep the Japanese one at some point in future, but I never knew how to apply to this so this has been left unanswered unless my mom submitted something on my behalf…

Based on this background, from my understanding, I have the following options:
1. Somehow recover my status as Japanese citizen through some paperwork and look for Japanese jobs that way
2. I saw that there's visa I can get if I am a child of a Japanese citizen. Will I be eligible for this even if I am ~30 years old, or is it only for children still under care? Can I use any relative's info or does it have to be my father's?
3. I work at an American branch of a Japanese tech company and have native language proficiency level communicating almost exclusively in Japanese at work, how much easier would the job search be if I manage to get visa through other means (assuming they are viable)? What are my chances without?
4. Although it's not set in stone, I do potentially have option to marry before moving for visa, but I don't really want to use my partner as a stepping stone to get into Japan and would like to move without.

So my questions are: what are actually my viable options? What would be the best course of action for me to take? If this is something I should ask a lawyer about, how should I contact one that specializes in this field?

Thank you for reading this wall of text, any suggestions are greatly appreciated!

by PresentationCool2174