Childhood promise

Because of a childhood promise, the lives of four people were destroyed. Can the mistakes be corrected?

Kevin: "Is it because of your promise that you left me? Is it because of him that you abandoned me?"

Hyuk: "It was just a child's promise. I never imagined it would change my life like this."

Xen: "I promise I won't be like him. I promise I will give up the world for you. Just stay with me, my little one."

Hangeum: "Admit it, because of me, your love is ruined, but I will make you fall in love with me and forget everything."