"Master Carl, this is Corbin, a knight of Hilfin."
Even with his tall stature lowered, Corbin was still above Carl, so he ended up kneeling on one knee and bowing politely to Carl.
Unless there are special circumstances, a knight does not kneel even to his lord.
They kneel when they are ordained knights and when they commit a very serious sin.
Nevertheless, he immediately got down on his knees upon meeting Carl for the first time.
'He wasn't treated properly as a knight, and he didn't receive any education.'
Carl realized that even though Corbin had been ordained as a knight, he was in fact no better than a soldier commander.
Would this help?
"Get up. Lord Corbin."
"… Yes, master Carl."
Corbin seemed taken aback by Carl's polite attitude, but soon stood up in front of Carl, shaking his knee and creating dust as if to prove his ignorance of etiquette.
"I'd like to hear more details."