Working two part time jobs instead of one full time

Hi, I thought I'd just like to get some bit of advice about what to do. It's a bit lengthy, sorry about that…

I am in a weird limbo kind of situation – I currently work full time at a Japanese company which I've been kind of struggling with on and off in terms of the working conditions and my mental health, but it's somewhat tolerable for the most part. In June I got a job offer to work in what I've always wanted since I moved to Japan, but the only issue is that it is part time. I did take the risk then and decided to go for it, and requested for my current full time if it were possible to switch to part time. I believed the reduced working hours might also help me deal with my own mental health which has been slowly getting worse over time.

Anyway, I requested for this back in June and, although it seemed like my managers were understanding and they said they'd speak to HR, it has been almost 2 months now and I still haven't gotten an update. Each time I've asked, the response was always that "it's in discussion". I didn't want to let the other opportunity slip, so I have been trying to manage both jobs hopefully until they give me some response. Even if it's a no, at least I'd know what to do then. But there's been no update.

The last time I asked about it, my manager switched the conversation to say that my work performance has been concerning recently, which was never mentioned until that moment, and I told him to let me know what I'm doing wrong. We had a meeting about this and after saying they are still discussing my request, he suddenly brought up if I wanted a raise. He kind of diverted the whole conversation to that.

I also had a letter from my psychiatrist which stated my condition and also that I wanted reduced hours but he didn't bother looking at it when I showed it to him. After that meeting I just kind of gave up asking about it, because it just seems weird to me that they'd take 2 months to answer one employee's request. It somehow feels like they're stalling until I stop asking.

At this point, I've considered resigning honestly, if I found another part time job. But I am also worried about how that would work, whether this would be feasible and whether I would be able to sustain myself with that. I don't know what to do but I'm honestly tired. I sometimes think I'm overreacting and I sometimes feel guilty for wanting to quit because everyone is generally nice here too.

I don't know how to make any of this work but I also don't want to let go of that dream job opportunity. I am taking risks I know. But I was already not really happy with my full time job and that alone was barely sustaining me each month anyway. I have been struggling with that too. I just want to get out of this situation and I don't know how.

Sorry for the long rant.

Edit: I'm on a humanities/ engineer visa valid until 2028.

by ria-bitar