For Japanese studios as said above it really depends on the company, some of the bigger companies have teams with almost only foreigners and they are no required to know japanese, but if you want to work for a company with few or no foreigners there is a very little chance to get let in if you don't know some japanese. As…
I can chime in here in regards to Japan. It really depends on the company, some require a very high level of advanced Japanese, and some require none at all. Generally the larger more famous companies require it to some extent.
Language certs are only somewhat important in countries where the studio language is usually not English, such as in China, Japan, etc. Maybe your Chinese / Japanese ain't good enough to write a resume in, but if you can talk to local staff it can be an advantage, depending on the job you're after.