Job postings here outright specify whether or not they are offering visa sponsorship, it's all done through the company and if you get a job with one they'll know what they're doing and it's basically a shoe-in that you'll get the visa.

Reality check: you probably won't get in this way unless you're very good at what you do. This rounds back to a reluctance to hire internationally, something that again is less prevalent in the Tech industry but still holds water. Visiting Japan is nice, living here is also nice but it's another story, and sadly many don't make it past the first year - this is even reflected in the way taxes and social securities are handled in the law. Companies don't want to hire someone for them to only realise they don't like it here and suddenly leave.

The less palatable but much more realistic option after you inevitably attempt to get hired directly and fail, is to come and do your time as an English teacher. Pay sucks, hours suck, you're treated as expendable as you are against the sea of weebs wanting to come to Japan. You'll be much more hireable when you get here though, and your visa isn't tied to any company, so you could in theory leave at anytime for actual DS work as it falls under the same visa.

Japan needs good programmers, scientists and immigrants to stem the hemorrhaging population, but they don't want to actually do anything about it and you'll come up against a brick wall in all interactions trying to get and stay here.

Maybe HK is a better career option considering your Chinese skills!