Mother, I'm Sorry

Gong Hyochan's world was turned upside down when he finally learned about his mother's terminal diagnosis. After all, they had no one else but each other in this whole world. He had always taken his mother's love for granted, but it was now too late to make amends. Or was it? A mysterious man approached him on his mother's bedside, offering to give his mother a new life at the cost of his own lifespan. The desperate Hyochan made the deal and 50 year-old Yeon Geum-ok was given a second chance in life. The catch? She was now younger than her own son!

(Source: MangaDex)