Something like 75% of development jobs in Japan are in Tokyo. When you're considering ones that will hire non-Japanese speakers, that probably goes up to 95%. That's not saying its impossible, and there are some opportunities available in the Osaka area. It seems Kyoto has a relatively vibrant startup community, and companies like Nota Inc which makes Gyazo is open to hiring non-Japanese. As for finding opportunities like that, the best way is coming here and getting involved in the community like HN Kansai or other more Japanese events.
Getting a visa as a developer in Japan is quite easy - so if you find a company willing to hire you, getting one should be straightforward. I don't know about response rates for companies - I've only ever applied to two companies in Japan - one who hired me and the other who didn't respond.
Node JS is getting relatively popular in Japan, and I've heard of a range of companies using it here. One strategy could be to focus on publicly demonstrating your node.js abilities with something like a blog, open source contributions, or giving talks at local developer meetups. If someone can take a look at a website or github account and think, this person knows node.js, it will dramatically increase your hire-ability both where you're living now and in Japan.