[Nyororin]

Please clear this up with me.

You say you will not be in Japan for more that 6 months , and that the course you will be taking is 5 months. Coming from the UK, you are eligible for a 6 month tourist stay....

So why should you need to reapply to extend the visa? Yes, you`ll need to extend the visa, but it wouldn`t be reapplying - it would simply be extending your period of stay...

I have never heard of a school asking a student to lie about the fact that they will be studying. In fact, lying would actually hurt your chances of having the 90 days extended as it would be hard to come up with a good tourism reason for needing to be in Japan that long. What school is this??

Tell immigration that you`re taking a short term Japanese course that is paid in advance, and show them the dates it is beginning and ending. That is the right way to go about things. There are tons of short term students who come to Japan to study Japanese on tourist visas. Getting a student visa just isn`t worth the time and pain if you are only going to be taking a course that fits within the tourist visa period.