HyukJae was a child when he first created DongHae and the Fabricated Dream World. All it took was a dream from the night before, a piece of paper, and some drawing utensils. HyukJae, however, didn't have a way to enter his world or see DongHae. So, he unknowingly created portals to DongHae, soon discovering that wherever his reflection was able to be seen served as a way to the Fabricated Dream World. Even his dreams were portals. From then on, young HyukJae would go "visit" DongHae frequently.

HyukJae created both his Fabricated Dream World and his DongHae. His World and DongHae changed according to how he wanted it. If he was depressed and needed his World and DongHae to match his mood, then they would go dark and gloomy until he decided he wanted it bright and cheerful. DongHae was HyukJae's perfect friend; he was able to suit HyukJae's every need every time, everyday. If HyukJae felt like being childish and needed a playmate, then DongHae was there. If HyukJae was going to go off on a rant and needed a mature friend to listen to and understand him, DongHae was there. He was there for HyukJae's every need; he would always be there; he would always understand; he was created by HyukJae and belonged to him. They were perfect friends for each other because HyukJae made it that way—but that didn't mean they didn't come without their ups and downs.

DongHae happened to come with own mind and his own way of thinking. That was the one thing HyukJae couldn't really control—the one thing from his whole entire World that HyukJae didn't know about.  DongHae wants to keep things this way, HyukJae knowing nothing about him, but even he didn't know what was really happening within himself. He didn't even imagine it was possible for him to "snap" and "blow up" as they say it. But DongHae isn't real at all. He was created, but something feels very different than before.

In his Fabricated Dream World, HyukJae controls nearly everything. It's all his and always will be. Unless he happens to forget for a certain amount of time. Or unless DongHae's personality takes an ugly turn and HyukJae decided to forget him, terminate him, kill him, locking him up forever in a very obscured nook of his memories. Or if he stops believing. Or if he throws away any of his drawings. Any of those could "kill" DongHae forever.

"We will be together. Forever and ever and ever."

But HyukJae's growing up and he doesn't have time to believe in his childish drawings. DongHae, meanwhile, is slightly changing into his own person and becoming real. Things change over time, but how they change is what makes everything else change. Whether it's a good or bad change is what creates the snowball effect and changes everything else.