[Maiken100]

Some really good advice from everyone, on almost every post. Don't think i can add much else except to emphasize that leaving things late could ruin your chances. When i say "late", what i mean is you can't predict the future and something might happen which could mean she either leaves the job or someone else asks her out and she says "yes". So don't take an age!

You have to respect her current relationship in order for her to respect you, so either be upfront about the whole thing, "tell her you'd like to take her out but don't know if she's in a relationship or not" that might save you any embarrassment if she says no, but "yes" would mean everything good!
OR just ask her out in work related way or say you need some help on something japanese related, be creative. There is always a way round!