Accidentally did factory reset on elecom router with docomo hikare

SOLVED
I accidentally factory reset the router and now have no idea what the login credentials were, turned the house upside down looking for the letter. Because it's Japan, docomo nor the provider have been incredibly unhelpful. Anyone have an easy fix?

Update: finally talked to someone useful at the provider company (Nifty) and they just sent a new router which took one day to arrive and 5 mins to setup.