extend visa in japan

I am going to study a short term course in Japan on 1st of April, and i wish to take the JLPT in Japan, which is held on 3rd of july. However, my visa allow me to stay in Japan for 90 days only. I would like to ask that is there any possibility that i can extend my visa for extra one week? And can i apply it in Japan?

What is your nationality and what kind of visa will you be on?

I am Malaysian. It's tourist visa.

When you are at the Japanese consulate,
either
1. inform the officer that you are going to Japan for a short term course and intend to stay on to take the test a couple days later. Show them your acceptance letters from the college and receipt for the test and return tickets. Request for a 93 days visa.
or 2. convince them that direct flights from a certain port- PEN, KUC or BKI to HND are offered on certain days eg., July 3rd and ask for a special visa for 93 days. Show them your return tickets for these dates, sufficient funds for the whole trip and proof you intend to return to your job/ school etc. in Malaysia.
3. In case of 1 above, you should provide strong supporting documents and a convincing answer if they ask why you prefer not to register for JLPT offered on Jul 3 in KUL and PEN (http://www.jlsm.org/html/jlpt.html)

Alright, really thank you so much for the information!!