I am a united states citizen studying in Japan, flying from Japan to Vietnam, this visa on arrival would work for me ?
You have three options to apply for your visa in this case:
1 - contact the local embassy of Vietnam in the US (New York/Washington DG, SF) to obtain your visa before you go
2 - Apply for a visa through the embassy of Vietnam in Japan (Tokyo/Osaka)
3 - Apply online for an approval letter from Japan to pick up your visa upon arrival.