BaekHyun discovers a time machine in his basement that has appeared to be there since forever. He wants to use it to go back and fix all of the stupid mistakes he ever made, but as always, EVERYTHING comes with a price.

Emi, sixteen years old, is having a tough time discovering new things such as the human life rather than her life right now as an angel in Heaven City above the clouds. Her life is usually odd since her best friend, Izumi, is the younger sister and guardian of her exboyfriend, and that she eats none other than taiyaki and melon bread only. She has a guardian, Momo, who looks like a teenager in appearanc