Donghyuck is the youngest omega prince of Chalrete. He has three older brothers, which means he is not in the running to be the next ruler of his kindgom. Knowing this, his parents decide to accept the first proposal sent Donghyuck's way. Despite being only 17,  Donghyuck is arranged to be married with the Alpha Crown Prince of Purene, Prince Minhyung. 

Donghyuck and Mark have known each other since they were small babies, but that didn't mean they liked each other. In fact, the two hated each other. They can't get along for some reason. Whenever one of them was asked they'd just say "I don't know, I just do." and that's how they lived throughout their lives. But when high school comes along, the two start to view each other differently.

Mark was diagnosed with Ewing Sarcoma when he was thirteen years old. He's been treated in the hospital for four years now, but there is little the doctors can do to treat him. Donghyuck was twelve when he found out he had Non Hodgkin Lymphoma. He shares a room with Mark, and has been for four years now. They both know they're going to die sooner or later, that's why Mark can't understand why Donghyuck seems so happy and free.