@Icese Blue Kayden explained that he wouldn't be appearing in his human form when prepping Jiwoo for his journey to Frame because that could put Jiwoo in greater danger (Kayden is a wildcard). Now if Duke actually managed to kill or harm Jiwoo irreparabily like the ass**** who broke Jiwoo's core when torturing him, it would be a different story, but Muse or Royst himself would probably have stopped it since unlike Duke, both of them respect Kayden (Muse's master in particular wants to recruit Kayden to work for their organization and that goes out the window if Duke got to carry out his wishes)