Corrin refuses to kill him, even though he's waiting for it, because she thinks it's odd that despite the king's orders he seemed reluctant to lead his troops into battle -- maybe even didn't want to win?

He says, "I value an oath I made long ago more than my own life." She always wanted to see the world outside the fortress, so one day he made a picnic and they took a few hours to explore! Illegally! They almost had him executed when he returned, but Corrin didn't let them.

That seems memorable! Oh yeah I did have a childhood friend named Silas

Corrin: So... if you'd die for me, you'll help me kill King Garon too, right??

Man, that is some... very strong friendship.