You and Xiao broke up 5 years ago cause you both were convinced that it wouldn't work out. You guys were still good friends, but it was just a little awkward. Soon, Xiao found out that you were with someone new. It broke his heart to see you move on, but he still smiled and accepted the fact that... you needed someone better..

One day you found Xiao talking to your significant other, and decided to eavesdrop on them

"...She's the best thing that you'll ever have.." Xiao says to them