Random twst thought
So you know how Yuu is from another world right? I know canonically magic affects them, but what if
What if Yuu isn't affected by most magic?
Like, the stronger ones still work on them, but they have high magic res so there aren't many that do affect them
Since they're from another world, their biology is bound to be different in some way. Otherwise that'll be a bit too convenient imo.
What if magic doesn't even really affect them at all? Maybe the nature of magic is actually a harmless force to them? Or maybe magic is like a virus of some sort that twst people are just kind of weak against. This would be a really funny scenario to explore honestly.
OR!
Alternatively, since I made a virus comparison, what if Yuu is like, reaaally weak against magic? They're not someone from twst, and a whole new type of energy that their body isn't used to might have a really big impact on them and easily harm them (if you want to go the angst route).
Or it might cause a severe allergic reaction because even if it's harmless, like healing magic (which I assume either replaces cells or speeds up their growth), even if it's supposed to help you, the fact that it's a foreign thing the human body isn't used to might make the body attack the new cells instead, and rather than heal the wound, it makes it worse.
Both are fun thought to entertain and since I have two Yuu OCs I might make them both have this muehehehehe