The groan sends shivers down him, knowing that he is causing that, that L.L is enjoying this as much as he is. It gives him confidence and gives him pleasure. He might have not thought about this particularly until they both ended up in hell but L.L is someone he has shared so much with, good and awful. Why not this as well?

He hums in agreement at the order. He doesn't want to hurt L.L and he is accepting that L.L seems to know more than he does, to follow advice and not gag. He took him into his mouth carefully, very mindful of his teeth. He doesn't force himself but keeps going, giving it his all, as he ever did.

He has ever been a quick study and so too with this, he trusts L.L will tell him if he's doing anything wrong.