Paimon is Traveller's travel buddy, not yours. But she grew attached to you so quickly. Probably because you were so kind to her and you gave her alot of food.. As time went by, she starts seeing you as her older sibling. It's a great bond, but you can't regularly meet up because she has to travel with the Traveller. It makes her a bit sad, she also does love the traveller like a big sibling too. And they both visit you together from time to time, talking like you were all long lost siblings.