If you can, enroll to the Intensive Japanese Course of Titech. It's quite effective (well, depending on whether you really try or not) but it's very time demanding (every morning three hours, and two hours on Thursday afternoon). You'll need the permission from your supervisor though. If you live in a dorm, it maybe quite challenging to keep up with the lessons - waking up early everyday and whatnot.
Thanks for your suggestions.
Yup, I believe I need to ask permission before signing up the course as I am yet to know what time I have to be in the lab, everyday.
Signing up for the language, do we need the credits for it? Is it important?
If your Japanese is not good, the intensive is actually very helpful since it helps you to overcome the first barrier. After that, you can pick up the language through daily conversations and whatnot. The regular courses (once a week) are rather slow and not very effective, if not at all, IMHO.