
It's called Red River or Anatolia's story, a shoujo manga I read long looong time ago lol. If you wanna read this, fair warning, be careful for a whole series of drama and tragedy. Or more like tragedies. But it's one of those manga that I don't think I will ever forget.
Here you can read it here in mangago:
https://www.mangago.zone/read-manga/anatolia_story/

Now I know that's not true, I mean she gave him his hand back and he's scared to let her near anything because he knows she's capable of making anything a weapon or to her advantage. I think it's more like admiration for someone who has proven beyond your expectations and you just want to do something for them.
Cain really reminds me of the 2nd ML in a certain manga. Same but also different, because you know what Cain? He truly trusts the MC (FL) in the manga. He trusts that the MC knows what she's doing, that she knows how to protect herself. You said you trust her, but do you really? You even make her extremely unhappy, and you call that protection?
That 2nd ML respects his MC so much even when he's drugged with something that would absolutely makes him act on his deepest desire, the drugged 2nd ML only just bow to the MC the entire time, that's how much he deeply respects the MC (´;︵;`)