Zhongli was your childhood friend. You didn't know that Zhongli actually likes you for a long time, it hurts him to see you're dating Xiao.

One day, your university was having a festival. Zhongli is going to perform with his friends, singing a song "The One That Got Away" by Katy Perry.

You came with Xiao to watch him perform. It was great, until Zhongli glances at you while singing the chorus "In another life, i would make you stay.. so i don't have to say you were the one that got away.."