— 𝐖𝐇𝐎 𝐈𝐒 𝐓𝐇𝐄 𝐌𝐘𝐒𝐓𝐄𝐑𝐈𝐎𝐔𝐒 𝐆𝐔𝐘 𝐌𝐈𝐍𝐇𝐎 𝐅𝐎𝐔𝐆𝐇𝐓 𝐀𝐍𝐃 𝐖𝐇𝐎 𝐋𝐀𝐓𝐄𝐑 𝐎𝐍 𝐓𝐀𝐋𝐊𝐄𝐃 𝐓𝐎 𝐈𝐍 𝐂𝐇𝐀𝐏𝐓𝐄𝐑 𝟑𝟓?

The guy later on appears to be nonexistent. This means Minho's mind made him up: first of all, because he felt like he was a bad keeper, but wasn't 'capable' of telling himself that, so his mind somehow made someone else up to tell him.

When the guy reappeared in the Map Room, trying to convince Minho to talk to Zee again, it was still a hallucination. Again, just Minho's mind, so obsessed with Zee that the only way of 'excusing' him to talk to her was making someone else force him.