In the first Persona 5 game, literally just titled, Persona 5, which everyone seems to forget about, the starting name was Akira Kurusu. I distinctly remember that because I've never read the manga, and I was angry they called him Ren Amamiya in the anime. I don't like the name, haha.
Which, unless Atlus changed the lore, is the true Persona 5. Royal is just an alternate universe. Still a fun game though. And good on Atlus for confirming the name.
