Moving there for girlfriend

I'm currently dating a english teacher who's there on a work visa. I'm a US citizen who receives a pension from the government. She plans on staying there a few more years so my question is what Visa should I apply for

There is no Boyfriend/fiance visa.

We don't know you and we don't have any info about you.

So here, take your pick.

https://www.juridique.jp/immigration.php

I do not think you have much change to get a visa, except a tourist visa.
If you want to stay in Japan longer you can move once to Korea and come back to Japan on a tourist visa.

Well you could :
A) get married
B) get a student visa and study Japanese (or something else)
C) come first as a tourist for 3 months and then do a bit of forward and backward (either with home or Korea/Taiwan). Just to find out if she is the woman of your life and get married then
D) search for a job of your own in Japan (depends on your skills vs available visa category and jobs.

I think dating a teacher is as tricky as clearing an exam, but I think conversation skills are the must in everyone's relationship and talking with a girl is a skill and everyone should learn it.

Could a resident Visa work. I'm to old to go to school again and I don't need a job due to my retirement income. I would be able to show I'm self sufficient

You would file for a K1 visa application,you would become their sponsor,once the visa is file,your future spouse would not be allowed to enter the US,until her visa is approved by ICE,I am not a lawyer Google K1 Visa card—

You cannot just move to Japan to live because you want to. You are here working or doing something under one of the allowable status of residence categories. Being retired (even if you had a million dollars), you can't just move here. After being here a few years, if you qualify for one of the long term resident categories, then you might be able to stay if granted (no guarantee of that either).

I don�ft think you�fre too old to go to school again. It�fs mostly younger people but you wouldn�ft be the only retiree studying Japanese in Japan. You would be improving on probably the #1 most useful skill an immigrant can possibly have in Japan and it�fs a reasonably easy route to mid-term residency. If you�fre doing okay for money then there is little stopping you.

If retired than it means this person has passed a certain age.
Even if you are skilled getting a job even in Japan on a certain age is difficult, almost impossible.

Most companies are trying to get young, and cheap employees.
Japan has a population which is 30% over 60 years old. Even those people cannot find work easily.

If you are �gwealthy�h you can apply for a long term (6 to 12 months) tourist visa. 30 million yen (about $275K) qualifies for it.
https://www.mofa.go.jp/ca/fna/page22e_000738.html