I though it was already know in their community that he was kaiden's disciple.

Most of them know he exist, few have met him

I think that while people are aware of Kayden having a disciple, only a few are aware of his name or what he looks like. Especially those outside of South Korea would probably have no clue about Jiwoo. None of the people in the party recognised Jiwoo and it’s apparent that they’re all from different countries. The only people who know who Jiwoo is Valtor and Arthur.