Consulting/FP&A in Japan without business Japanese?

I'm writing this because my girlfriend and I are in a bit of a situation, and I'm looking for options. My girlfriend is Japanese and I'm from the US. We've been together for about three years: the first two were in the US, and this past year has been long distance. We want to get married and be together, and we've been considering options for both me moving to Japan and her coming to the US. She has a once in a life time career trajectory in Japan, and I really don’t want her to have to give that up. Realistically, it seems more likely that she would move here, but I want to see if there are any ways I can do that in my current field or something related.

I currently work in financial management consulting in the US for a boutique consulting firm that doesn't have a presence in Japan. Like 90% of what I do is financial modeling, developing rate structures for clients, and evaluating the financial feasibility of investments in client operations. As for Japanese ability, I’m on the lower end of N3. I can hold conversations without much issue, though I make small mistakes here and there that people usually understand. I’m not close to business level. I don’t have any problem with the idea of working in Japan, but I don’t necessarily see it as realistic given my current Japanese level and the fact that I’ve never worked there. I've heard people talk about transferring internally to a Japanese branch of a multinational, but I don’t know much about how that actually works. I’ve considered switching to a company like one of the Big 4 and then trying for an internal transfer, but I’m not sure if that would be possible given my Japanese level or what kind of timeline that would involve. I know that exists but I've never talked to anyone who's done it.

I guess the reason I’m writing this is to get some outside input and hear other people’s thoughts on whether there’s a way for me to work in consulting, FP&A, or something similar. If I don’t need sponsorship but also am not at a business level in Japanese, is there a realistic possibility for me to enter those fields?

by Career_penguin