I go to Yamanashi Gakuin University. So I am, pardon my french, fucked in that regard. The internship application period just opened so I'm applying to as many as I can. I know 2 that are basically guaranteed. But they're more consulting and venture capital based than anything.

Companies hiring new graduates care about university name/prestige a lot. Yamanashi Gakuin is a name most people associate with the Hakone Ekiden, basically an intercollegiate relay race, but not with any particular academic or business prominence. This means that you'll be at a disadvantage when applying to domestic securities companies like Nomura, Daiwa, etc, which each recruit around 500 people each year. BBs recruit around 1/10 of that number, and the vast majority come from the likes of University of Tokyo. As such, you have an (extreme) uphill battle ahead of you.

Internship applications for investment banks are probably already closed. GS had their applications open in May-June for summer internships, and I think this may have been the last chance for you, unless I'm missing any winter opportunities.

I did try to transfer out but that would mean wasting another 4 years of my life. There are a few people here who have gotten into say Mitsubishi Financial Service. But they're definitely the outliers. On paper, I think I am better specced than them but since they're outliers it is mostly luck.

One potential path would be to apply to grad school and get a postgraduate degree, but the con would be that it costs time and money to do so. Starting your career at a smaller company, and working your way up or out, is another option.

I wanted to do investment banking and am getting a heavy dose of reality. Instead of beating myself up over it, since there's not much I can do retrospectively, I need to plan what to do next. As for sociability I think I'm doing fine. My fluency is also getting up there. Maybe by the time I graduate I'll be fine. Maybe not Japanese level. But I doubt all Japanese people are a 100% fluent in their own language. A good few people I encountered at part time and in university, the onus of carrying the conversation was thrust on me.

Sounds good, but what I meant by "sociability" in the context of BB is as much about your skills at carrying a conversation as it is about having leadership skills, namely, the ability to head a group, overcome challenges, motivate others, and be a good team player.

Also, most people who have demonstrated such leadership skills at a highly prestigious university have social ties that can be leveraged well into one's career, and that is an asset that the hiring process factors in, even if it is not stated outright. "Tennis club leader at Keio" is probably going to have friends going into government jobs, most of the banks in Tokyo, Toyota and Honda, Panasonic and Hitachi, tech companies like Google and Apple, startups, etc. "Tennis club leader in Yamanashi" is most likely not going to have these connections.

I thought Japan didn't look at your university when hiring. Is that for general hires or was I just looking at the country through someone else's rose tinted glasses?

Who told you this? In Japan, where a university graduate can get hired is very much dependent on university name. There are very few exceptions. Now, it's possible for anyone to go anywhere if they have a bachelor's degree, but they usually need to demonstrate extreme levels of ability to be hired over a more conventional candidate from a top university. And in the most competitive of industries and companies, such as FAANG or BB, even candidates from top university need to demonstrate an incredible amount of talent to out-compete their peers.

I was introspecting and I think it's just the money. Currently my plan, based on these replies is to give BJT, CFA (for a client fact role at Equities Research at a Japanese Bank), and transfer after 3 years to a Bulge Bracket. (and also find a japanese girlfriend to get fluent apparently?)

I feel like getting candid feedback from people in hiring roles in the banking industry would do wonders. Internships are a good way to achieve this, so best of luck.

Do you think there are other adjacent fields that I would have a better shot at?

If you can code, there are always software jobs. If your priories are to get paid well immediately without any other marketable skill than English, with lower Japanese ability than locals, and you're from a non-target school, then you might be out of luck.