Anyone can see a soul once it's been manifested physically, but you can't make it appear without magic- so a human could see what their soul looked like, but they'd have to have a monster pull it out for them, they couldn't make it happen on their own.

...Well, most humans. I've heard there were a rare few that had magic, that's how we were sealed behind the Barrier in the first place, but it's so uncommon as to be nearly nonexistent, especially in the modern day. No one's seen a human mage back home in centuries, at least.