One of the interesting oddities of Japanese is the meaning of the word "yes". On the face of it "yes" would normally be inferred to mean, well "yes". But not necessarily so in Japan.
Here "yes" can literally mean yes, no, maybe or even "I'm sorry, I haven't a clue what you're saying". You can imagine the depths of the confusion this can lead too especially when first encountering the word "hai" (the Japanese word for "yes").
The yes and no meanings typically happen in business. A question asked in English may genuinely receive a positive confirmation. However, and this is often the case, it could be a strategic yes, where the answer is actually no but everyone in the room is working out exactly how to break the bad news.
Added to this, there is often a concern about clarifications. Asking a Japanese colleague "do you understand" will invariably illicit a positive response however the reality could very well be "may be, I'll have a think" or even "what did he say?". Especially in a group it would be rare for someone to actually put their hand up and "Sorry, didn't get that. Could you explain again?"
And then there's the I haven't a clue what you'er talking about. If someone says "hai" but with a distinctly upward inflection and then just stands there looking at you, you need to try again. This wasn't a yes confirmation but more a statement of "what did you just say?".
Oh, and don't even get me started on the answers to negative questions. I'll save that one for another day.