On international models of the GS4, NFC-A secure element is on-board the phone with the antenna in the battery. On the SC-04E, this set up is replaced with a FeliCa secure element for domestic transactions. Therefore the NFC-A element on the SC-04E is included in the SIM card.
What this means is, if you unlock your NTT Docomo Galaxy S4 SC-04E, and attempt to use it with mobile payments overseas, you'll have essentially two options:
- pay Docomo data roaming rates
- swap sims and reboot every time you want to do a payment.