Over 90% of the foreigners working in Japan are not teaching English. (The government here keeps track and periodically posts statistics in Japanese.) However, yes, most of these foreigners have at least intermediate Japanese. There are exceptions--particularly if you have knowledge of programming languages and/or experience with software development, database administration. (If you are proficient, say, in C++ and Java, know how to work with multiple operating systems and understand how anti-virus and network security systems work, then the Japanese language requirement--even if listed in the advert--is often waived.)
Ads can be found at Daijobs --
https://www.daijob.com/en/ -- and a few other places. Here's another hint: If you do a search in English for the desired position on Yahoo!JAPAN, you will often be able to find job adverts--many posted only on company websites--from a variety of companies in that field. While a number of ads will be for places outside of Japan, many (most?) will be Japan-based. (The search engine can be finicky at times until you get used to it.)
As with a job search anywhere else, look through the available adverts, apply to any job not listing a Japanese language requirement, and keep your fingers crossed. That said, you should be aware that there are a small number of scammers out there--never pay money to any private agency to get hired and/or to facilitate getting a visa. Finally, regarding commission-only positions, I personally would recommend against them. The English-speaking population in Japan is quite small, and many do not have significant sums to invest. Given this, unless you are fluent also in Japanese (and/or Chinese/Korean), the pool of potential customers is often too limited to make a decent living just off commissions.
My two yen, anyway.