extending a tourist visa?!!

hello everyone....
i'm actually planning to go to japan for a period of 3 months to study at a japanese language institute, but i got a problem...
i don't really know if i gotta apply for a student visa or for a tourist one....
i'm going via a language school and i heard that i can't apply to a student visa for a language school... aaaaaand the tourist visa lasts only for 90 days, but i may stay more, maybe 91 or 92, i still don't know when my courses will start and end........
so i was wondering that if i got a tourist visa for 90 day can i extend it in japan for 5 or 10 days (as i'm from a syrian nationality) ???
i'll be waiting your replies, i really need an answer....
thanks in advance

Syria is not on the list of visa waiver agreements with Japan, so it will be entirely case by case whether immigration lets you stay longer. You will have to show a good reason and proof that you can support yourself during that time.

Are you sure a language school doesn't qualify for a student visa (either of the 2 types)? It would make things much simpler.