There is a special visa for highly skilled immigrants. If you hold an advanced degree (MSc or PhD), have a highly paying job offer, and are young, then you'll get a visa easily and there is a quick path to permanent residency (after 1 year in the best case). If you're not highly qualified, then I guess things are more difficult. From what I know the rules are straightforward, reasonable, and the visa application is processed quickly. My perspective may be limited, so take everything I say with a grain of salt.

I don't know much about job market, but I met many expats working as software engineers and they didn't speak any Japanese.