Towards the end of the 1st opening of "That time I got reincarnated as a slime", who is the character Rimuru fights (details and link provided if you click)?

The link is this:
https://www.youtube.com/watch?v=u67olZLcDPc

The guy battles Rimuru at 1:11. It’s a swordsman in white dress. Obviously to find it you have to use the fandom section here: http://tensura.wikia.com
I tried but couldn’t find it. There are too many characters! Maybe you’ll have more luck.