If you really want to.
If you do it at all call them styles, reading about the 'stances' in SA is weird because they aren't stances, they are styles.
Personally that's not my interest, but maybe other people like it, or you do. Write what makes you happy.
And, small note that you are welcome to throw away, can Corrin use his sword as a back up weapon? I know it's weird in fantasy but historically that's how it was, there is the Japanese(I think) proverb that goes something like "A swordsman, must be three times as skilled as a spearman, in order to defeat him." for a reason. Just small things that bug me about fantasy, but that is something that probably no one else will ever care about.