Cellphone in Japan - SIM or Buy?

I will be studying in Japan for a year from this September and I am a little confused about what I should do for a cellphone.

1) I currently have a Samsung Galaxy S3 that is in horrible condition that I could replace with a new one and unlock before coming and then use it with a SIM. However, I'm not sure where to find SIM options that would be better for a yearlong stay in Japan. Also, I've been told that if my phone doesn't have the certification that all Japanese cellphones do that they might not give me a SIM.

2) I could buy a cheaper Japanese cellphone (prepaid) and then have my own North American smartphone for wifi opportunities; though I know that this a rare thing in Japan.

3) I could get a Japanese smartphone on contract and just pay off the phone when I come back to Canada after my year. Though I am not sure how well Japanese phones work in Canada...there is a chance that I will go back to Canada following my graduation from university.

I am just not sure what option would be easiest for my life in Japan or benefit me the most. To be honest I'm a little overwhelmed trying to figure it out when I cannot find the information that would help me.

Looking forward to hearing peoples thoughts!

1) I currently have a Samsung Galaxy S3 that is in horrible condition that I could replace with a new one and unlock before coming and then use it with a SIM. However, I'm not sure where to find SIM options that would be better for a yearlong stay in Japan.

There are several options depending on what your needs are. Basically do you need voice or will data-only suffice?

Also, I've been told that if my phone doesn't have the certification that all Japanese cellphones do that they might not give me a SIM.

The certification sticker just means that it has been tested and should work in Japan. But most will still sell to you if your device lacks the sticker. They probably just won't guarantee that it'll work.

2) I could buy a cheaper Japanese cellphone (prepaid) and then have my own North American smartphone for wifi opportunities; though I know that this a rare thing in Japan.

That's an option. And free wifi isn't quite as rare as you might think. Check out this page for more info:

http://www.japan-guide.com/e/e2279.html

3) I could get a Japanese smartphone on contract and just pay off the phone when I come back to Canada after my year. Though I am not sure how well Japanese phones work in Canada...there is a chance that I will go back to Canada following my graduation from university.

Also possible, although you may have trouble depending on the length of your visa. Generally you'll get more full featured service, but at standard prices.

Certain phones can be unlocked to use in Canada, but it depends.

I would recommend getting an unlocked iPhone since they support a lot of bands when you're looking for a phone check if the phone supports the bands for the carrier you want to use. I would get a Canadian phone if I were you make sure you get a phone that has no affiliation with a carrier if its android because sometimes you can't update it if you are not on that network.