Old account recover for my friend

Hello my friend used to play Clash Royale in 2017, he had a fairly big account with many legendary cards. He has recently started playing CR again, and he would be blessed if he could recover his old account. His name was Nightxhun, King Level 11 or 12. Back then there was no Supercell ID, so no way recovering it that way. He remembers he was connected with google play, but he don’t remember which Gmail address that was. That being said, is there a way to find out with which google play account he was connected, because in doing so he could sign up into that Gmail, since he still remembers the password, but not the email itself…
Thank you and have a wonderful day!

Not possible. RoyaleAPI does not assist people with recovering their accounts.