Zein didn't recognize the man right away, but as he looked at Arden's clique, it reminded him of the group of guides who used to antagonize him in Umbra. He observed the members one by one, and as his eyes fell into the green uniformed man in the back—lo and behold; the leader of Umbra's clique was right there.
Nora was a guide who came to the red-zone just after Zein's initial ten years slave contract ended. Unlike Zein, his C-class license was a legitimate one that he acquired before ended up in Umbra. Zein had no idea whether the man was kidnapped or came willingly, but he remembered that Nora became the Guildmaster's pet soon enough, leading the group of guides with like-minded coquettishness like a queen—or rather, mistress?
He remembered the man as the one who actively tried to demean him and spread words that Zein was no longer able to guide well, though it helped him end his contract anyway, so Zein didn't really care about that.