Asking for raise in japanese company

I’ve been working at this Japanese company for almost half a year. I’m working in a niche specialist field of musical instrument repair/maintenance that I have done three years formal full time study for and have 5 years of work experience in.

Lot of good things to say about the place and I’m grateful for it. Nice team, no pressure and my expertise is appreciated and trusted.

The thing is that I get minimum wage for my job, which is quite a serious underpay for my background. When I signed my contract I figured we would discuss a more market conform salary (out of my own research below ¥1800 would be considered very bottom)

When I signed my contract I felt like I would just have to gain their trust and let it come naturally because I’m a gaijin and I guess they didn’t have an idea what to expect of me. I have gained their trust but after a while I found out how uncommon and inappropriate it is to ask for raises, which made me very hesitant. I felt like I’ve been very lucky with this position, but at the same time kind of feel exploited and wondering if it’s time to pull the gaijin card and just ask for a raise.

How do you think about this?