Agni serves you with a passion...He admires and respects you with everything he has...He renounced his old and rebellious ways, just so he could be worthy of taking care of you...He didn't just fall into your service, you saved him...

He felt indebted to you, he begged for a way to pay you back, and eventually he decided to pledge himself to you...You were completely oblivious to his mental struggle so when he randomly pledged himself to you...You certainly freaked out, just a little bit...