I’d suspect that job opportunities in QA are more limited than that of doing software development.
To do QA well, you need to be able to think like a user would. Most companies in Japan create software for the domestic market, and so you’d need to be able to think like a Japanese user would, something that’s quite challenging to do without the cultural background.
While ideally you should still have the same thinking as a developer, I think there is a bit less cultural context needed in coding. Companies will often formalize requirements, and if a developer is presented with some sort of spec, they can get away without understanding the nuances of Japan.
I also think QA isn’t seen as a particularly valuable function. QA prevents loss, but doesn’t produce any value in and of itself. That perhaps makes it harder for companies to think they need to hire exceptional QA people, and so will be less willing to take a chance on recruiting someone from abroad.
What’s more, as a general trend in the industry, I see a move away from having a dedicated QA team. Rather, that role is taken over by developers doing automated testing, and user experience designers who are concerned with how people use the product. This is based on my experience primarily with web startups though, so in other industries, it might be different.
One other thing is that if you are applying for roles that require Japanese, N5 doesn’t mean anything. For companies looking for Japanese skills, they’re typically looking for something around N2.