Well I was just wondering who has lived in Japan for either work or school or who IS living there and how they like it. I was thinking about going to Japan on exchange but the idea of being away from home for 5-10 months scared me.
I was a student in Osaka, and now I'm living and working in Wakayama. My advice to you is.......GO!
You're 16, that's perfect. Your friends will be there when you get back. More importantly, you'll make great friends here in Japan. When I was 16, I traveled to Thailand and Sri Lanka by myself, and I tell you, it was one of the greatest experiences of my life. GO NOW! You never know what will happen in the future that might keep you from never getting to Japan. Go while you can!
I was in Japan on exchange as a 17 year old for a year, went back to Japan a number of times, and now live and work in Japan.
I would say go. This sounds like old-person advice, but you have the rest of your life to stay at home. Even if you go to Japan, hate it, and never go back, you will have tried and will have changed how you look at the world (hopefully for the better). Going to live in a foreign country can really change your outlook, direction, and perspective on life. If you hate it, at least you will be comfortable knowing that home is where you belong. If you don't go, won't you always wonder what might have been?
And yes, your friends still will be there when you get home. And yes, you stand the chance to make wonderful friends while in Japan. My old host family is like a second family to me and going to their house (about three times a year) feels just like going home.
Find a good program and go for it. If it is a max of ten months, you should make it just fine (plus being in Japan is a great excuse for friends and family to come visit you when they might never have had the desire to travel overseas). You are not tied down with a job, a spouse, college, taxes. All those fun adult things you can start anytime? When else can you try something out no-strings-attached than when you are a teenager (aren't I right here old folks)?