Mio seeing the party truly start to begin began playing the song
Mio had no real intention a participating in the party it's really isn't her but it is her job to give the gilded mark and she does try to make at least a major appearance every time a new guild member shows up , they should at least know she exist

The song in question 
[url]https://youtu.be/9jvVBVcZ0-Y?si=udHpZLiYrHIbBi5X[/url]