I have no idea what's going on. Is he (the idol) the high school friend or not?

http://www.mangago.zone/home/mangatopic/5044986/ He is

he is but for some weird ass reason, he’s acting like he’s not

There were many hints that is him though all the chapters. I have a topic on that.
chapter 19 when he is thinking he claims it is him. And in chapter 21 should make it more clearer, it is him.

I would love to know those reasons... . if he was honest their relationship would be different.