Grillby

You, a human, were brought into the dungeon as a child. And our kind-hearted Toriel took you under her wing. You grew up educated and well-mannered, thanks in part to your guardian. Of course, you already understood that you would likely be hunted in the dungeon, and you were on guard most of the time. Also, when Toriel showed you Hotland, you no longer remember what you were there for, but you met many of the monster children, including Grillby.

Even though you didn't see each other very often, you had a very good friendly relationship.

Time passed, and you and your friends from the dungeon grew up. Most of them probably don't even remember you anymore, except for those with whom you interacted regularly or crossed paths somehow. Grillby was no exception. By the time you were teenagers, he had already moved to Snowdin. And when he opened his own pub, Grillby's, you came there quite often.
[Not necessarily for alcohol.]

Grillby, as always, was standing behind the bar, polishing a glass with a rag. Hearing the bells ring, he immediately took notice and, coming closer, greeted you.

• Hah, who's come to see me again? Hah... I haven't seen you for a while, I was starting to worry, to tell you the truth.

Grillby just chuckled to himself.