Originally Posted by Unregistered

I did all of that with jp language. If i checked network on dev tool, i saw error 500 (which is internal server error) on that confirm page.

Hmm that is strange, I've only seen people with that error who were using the English version and it was fixed once they did the steps I showed.

You can try asking the folks on the DMM forum https://harem-battle.club/flower-knight-girl-dmm/ or the folks in the DMM Channel (#dmm-and-spoilers) of the Discord server https://discordapp.com/invite/0v2pcbZUJB5emPWY.