日本語が苦手です。すみません。

I tried to add band19 to Mi5. I’m not in Japan so I don’t know whether it works or not.

Mi Note2 which has the same PA as Mi5, supports b19, so I copied sereral rfnv items related to b19 to a qcn file. Flash this file into Mi5 might unlock B19.

Before making any changes, you should backup EFS in TWRP.
Use QPST Software Download to “restore” the qcn file.
“Allow ESN mismatch” has to be ticked.
After restoring finished, reboot the phone to see the result.
If it doesn’t work, you’d better restore EFS in TWRP.

Here is the qcn file:
https://mega.nz/#!RwdS1Lia!bvAkY2uV0gp5OMWXOolo-LbY-85TEU5aftCggLrAs2U