You need to start learning Japanese now.

“If you talk to a man in a language he understands, that goes to his head. If you talk to him in his own language, that goes to his heart.” said Nelson Mandela. This quote couldn't be more true in Japan, where context and inter-personal relations play a key-role in landing a job - or not. 

Japanese language is considered as a hard one for many reasons: kanji, grammar, kanji, homonyms everywhere, kanji, politeness levels... yet it can have some incredibly easy aspects such as pronunciation! Japanese is a very musical language and pronunciation does not take much time to be mastered, compared to Turkish or Chinese for example, if you're serious enough about it. 

Japanese is also pretty straightforward when it comes to articles or plural: they do not technically exist... as well as the future tense. Yep, Japanese's punk, No Future.
Japanese language has also a particular learning curve : grammar is puzzling a first but once "the code" is debunked, it is surprisingly easy to navigate in and you can level up in the language in the blink of an eye! 

So, what about the consequences of learning Japanese when looking for a job in Japan? 

Actually, it makes things much more easier and, with equivalent skills, you are pretty sure that the candidate with a better understanding of the language will be chosen. It may sounds extremely logical but most of candidates nowadays don't speak Japanese and speaking Japanese (or even trying to) can be the key to your dream job in Japan!

You will be also more comfortable with your office's social dynamics: understanding the language is tightly linked with the understanding of the culture. In a blink, you will grasp who's the boss and who's the rookie thanks to your knowledge of Keigo, the politeness levels.

You don't need to speak a perfect Japanese... Nobody should expect that from a non-native! What will be your pass card is communication skills! As long as you can communicate in Japanese and make yourself clear and understand others without  any long pause, that's enough. There is ways to cope with language difficulties and smoothen a conversation: reformulate, ask again or simply ask what the missing word mean... Don't panic! Stay calm and go with the flow. 

By the way, did you know that if your profile is written in Japanese, it has way more chances to be seen by recruiters? Try it now and get closer to the career you want to build in Japan!