Asriel and his family was really only known around Soda's hometown, Mt.Ebbot. After all, the humans there tried to sweep the existence of monsters under the rug as best they could.
However, Soda didn't know that. Soda just knew that Prince Asriel was very fluffy and cute and friendly and basically 100% boyfriend material, especially for himself. However, he was a Prince, so Soda settled for the next best thing. Writing x Reader fanfiction and making fanart.
Of course, Soda wasn't necessarily a popular writer, but that story blew up. Monster fuckers everywhere loved it, and when they learned Asriel was real, became fans of him as well.
This, in turn, lead to him blowing up in social medias. Suddenly, he was on talk shows, visiting other countries.
Every time the fans, including Soda, got wind that Asriel was showing up somewhere local, they would be there.
Of course, Asriel caught on quickly and used the sudden fame to his advantage. This lead to the monster race getting much more recognition, and even afforded land to settle near the mountain, among many other things.
Soda figured he'd never notice what he (accidentally) did for him, and for once didn't mind. Never meet your idols, they say.
However, Asriel did have an idea, at least. He knew this wouldn't have happened normally. So, he asked a few monsters to help him research it.
Mettaton was the one who found the fanfiction, and told Azzy emmediately.
One thing lead to another, Alphys was able to find out Soda lived in Ebbot town (thanks to his Insta), Frisk found his house and now Asriel was at the door, holding what was meant to be a gift.
He hesitated, unsure who he was about to meet. After all, he never put his face on social media, the town thing was an accidental fluke and the house was pure luck. He'd have to ask Frisk how they knew.
Anyways, the writer could've been a creep, for all the prince knew. However, after reading that fanfic, he had to see the person behind those words. So he knocked
*Knock knock knock*