Um, well, they are two very similar people so not knowing would not make sense, actually.
NO idea what you just said! who? not knowing what? jeez. could you be any more vague? Are you talking about WooJin and Joohoon? They're so unalike that I fear for your sanity. you might have accidentally taken the brown acid before you read my post. Joohoon has absolutely no way of knowing what's on WooJin's mind unless something made that possible. They cannot read each other's minds. It's not that kind of story. Please make sense.
Whoa there, lol. If Joohoon had a lot in common with Woojin, then he could make that inference about Woojin's behavior. "If it was me, I'd never let go of that cutie." That's what the first Anon meant. I do agree that they aren't alike. So that's not how Joohoon would have known Woojin was protective of Taemin. He knew because Woojin hit him at the karaoke bar when Joohoon tried to assault Taemin. Woojin made it clear that Joohoon could not get to Taemin without going through him first. But, yeah. Woojin and Joohoon aren't alike at all. Joohoon is like...loosey goosey about his behavior, planning, and motivation. Woojin is calculated, controlled, and precise. To me, they are opposite. It's interesting how Haribo wrote their characters, though. I think she intended for us to think they were more alike at the beginning, and that a lot of the plot twists hinged on the fact that they are actually very different.
Haribo told us that Joohoon and WooJin were teaming up in Chapter 55 or 56 when Tae Min was brought to Joohoon by the guy who tried to bash Tae Min in the head. Joohoon told TaeMin that WooJin would not be separated from TaeMin no matter what or how. How did he know that? He couldn't have unless He and WooJin had somehow been communicating with each other.