Does any US iPhone 5 work?

I have wanted to buy an iPhone 5 for a while now, but since I will be studying in Japan for a year in the fall I want to make sure that such an expensive phone will work over there. I found a couple threads regarding this topic, but they were about the AUS iPhone 5 working.

I was considering Virgin Mobile's iPhone 4S because of how cheap the monthly plan is, but they already told me that there is no way this phone will work in other countries.

I then considered Straight Talk because their monthly plan is also cheap. I read that since you pay the full price of the phone, it comes unlocked, which I believe means it can be used by other carriers? If so, would that make it able to be used in Japan?

If I read previous threads correctly, a US iPhone 5 will not work. If you connect to wifi, internet and apps (Skype, WhatsApp, Facebook) will work though.

I have wanted to buy an iPhone 5 for a while now, but since I will be studying in Japan for a year in the fall I want to make sure that such an expensive phone will work over there. I found a couple threads regarding this topic, but they were about the AUS iPhone 5 working.

An Australian iphone5 will work in Japan with international roaming, but it is extremely impractical and expensive. If you get a factory unlocked iphone 5 you can use it with a Japanese service provider. Jailbreaking is currently not an option.

I was considering Virgin Mobile's iPhone 4S because of how cheap the monthly plan is, but they already told me that there is no way this phone will work in other countries.

Hmm, I don't see them selling the 4s anymore. It should work as long as its post paid service according to virgin mobile's faq:

https://community.virginmobile.com.au/t5/Phones-knowledge-base/Global-...

I then considered Straight Talk because their monthly plan is also cheap. I read that since you pay the full price of the phone, it comes unlocked, which I believe means it can be used by other carriers? If so, would that make it able to be used in Japan?

I think that should work if the phones are indeed unlocked.