This isn't an update. I'm just here to clear things out for you people that are confused.  Think of the recent flashback that Minyoung remembered about her childhood. 

This is a question you guys should be asking: Why was he leaving the school?

That would lead you to more questions and then it will be partially the answer to if he was real or not.

From the flashback, Sehun gives her a paper crane on his last day of school. So when the future came, of course Sehun wouldn't know who Minyoung is, maybe can Minyoung if she recognized his face. He sees the origami that is attached to her keychain, so then he recognizes her.

the question is, is Sehun real? He is. If you'd just think about it, Sehun could be leaving for many reasons, but in the end they could come back to their hometown. Minyoung gets the illusions because remember when she was young and had a crush on Sehun? One of the reasons why. But she doesn't know that. This is getting more confusing for me to explain so let's get to the answer. Sehun is real, but Minyoung is only getting illusions before he comes back in real form. They knew each other as children, and yeah. 

This is the last update for this story. c;