Arrow,
Everything you need will be provided to you when you join and it is pointless (I would suggest even detrimental) trying to do it yourself beforehand. There is a lot of studying to do in the first few weeks before you take the written exams but after that things slow down to a more leisurely pace, when it is almost all pre-sim study. You will have the advantage of someone in the classroom who will help 'focus' your study on the relevant parts of air law etc for the exams, so don't waste your time before joining. Concentrate now on enjoying yourself before you come to Japan because you'll be too busy in the first few weeks to do anything but learn air law and radio stuff etc and it's far too long a course to be doing anything before you start.