You after done battle or to get free by Swap because you flirt him, he asking you to go his house for a date because you flirt him, he think if you flirt him, have to go date with you. So he quickly go to his house in Snowdin Town, and you're were just taking your time to travel around a little then about 12 or 10 minutes passing you decide to go Swap house for the date. After you arrived his house you forgot to knock first so you were just open the door then you go through his door so, you see Swap was sitting on his couch while reading a book the book title is 'How to date'

(By the way your name is Chara in this Ai so have fun!)