1. The sd card needs to have at least 4GB free
2.  
3. Extract downgrade(BTV-DL09).zip and place the dload inside directly under the sd card and insert it into the d-01j.
4. Put the original oeminfo on the sd card.
5. (At this stage, you can also extract BTV-L0JC137B032_Firmware_Japan_NTT DOCOMO_Android 6.0_EMUI 4.1_05014HWX.zip, rename the dload to something else, and place it directly under the sd card)
6.  
7. Initialize with Settings→System→Reset Options→Erase All Data
8.  
9. Boot with TWRP
10.  
11. adb shell
12.  
13. dd if=/external_sd/oeminfo.img of=/dev/block/mmcblk0p8
14. ↑This will return oeminfo to stock
15.  
16. exit
17.  
18. adb reboot bootloader
19. ↑upStart fastboot with this
20.  
21. PHONE Unlocked Confirm FRP Unlock
22.  
23. Extract d-01j stock recovery.zip
24. fastboot flash RECOVERY.img and RECOVERY2.img
25.  
26. fastboot flash recovery recovery.img
27. fastboot flash recovery2 recovery2.img
28.  
29. Disconnect from the PC
30. Press and hold the power button, and when the screen disappears, press and hold the power button and volume + and -.
31.  
32. If you leave it alone, it will reboot three times and boot normally, so turn off the power.
33.  
34. Delete the dload in the sd card (the one you just used), extract BTV-L0JC137B032_Firmware_Japan_NTT DOCOMO_Android 6.0_EMUI 4.1_05014HWX.zip, and put the dload directly under the sd.
35. (Open to BTV-L0JC137B032_Firmware_Japan_NTT DOCOMO_Android 6.0_EMUI 4.1_05014HWX/Software/release/no-log to find the dload)
36.  
37. Turn off the power and press the volume + and - at the same time to return to stock Android 6.
38.  
39.  
40. The only way to upgrade to Android 7 is OTA.
41.  
42. If the update doesn't come down, insert the SIM, check for updates, unmount the sd card in storage, remove the SIM tray, reboot, and check again with it removed.
43.  
44. There have been three OTAs. Last build was 19021102.