"That's a really noble thing to say." He smiles a little, even though he still looks a bit sad as well.

A wound in his heart? Guess that might be why he experienced a lot of pain when he saw Cyntia get attacked. It seems likely that he lost someone important to him a while back. Erasing his memory doesn't sound like the right thing to do, but getting upset at Diarmuid about it won't help anyone. It's not his fault.

"...Were you a knight when you aged up?"