Darius's biggest hope for anything he taught Kamui was that it's okay to let go of your past and just live your own way.

The kid agonizes over what he considers to be his duty- avenging his destroyed clan. His retainers died to keep him from harm and he feels an obligation to avenge them... But nothing's going to bring them back- and he's twelve, what's he supposed to do?

Also, Darius makes sure to teach the kid a thing or two about engineering and metallurgy.