Wait doesn't the EVO have a hidden sim card slot?? I remember reading on it or saw it from the tear down they did. Could be wrong but about 90% sure. What I don't get is why these phones still don't come with a sim card slot. I for one travel quite a bit but always have to end up using my gf photon. I'll search and post the link if im correct.
I know Japan networks use GSM, pretty sure China and HK are the same. With international roaming the EVO LTE should work, at least for voice calls and text. I was there a couple years ago with a Hero; it worked intermittently. Any time you have wifi available that should work too.
Bear in mind international roaming can get really expensive. Might want to look into getting a GSM based Sprint phone; a Sprint store may have specifics on how to do so. Also recommend you check into a prepaid phone on another network at least for calls and text.
As kg4icg stated, i believe the EVO Design was the only EVO that had world capabilities. I wish Sprint offered more world phones.To my knowledge these are the other world phones on Sprint, the Photon and iPhone 4S.