[Frontier]

My understanding is that Sannoh, the chef, was driven to prove that all the work he and his sous chef's put into their work mattered by pushing himself to make a meal for the conference and fighting through his own illness. But that illness and his own doubts made him afraid of ruining it, which lead to what the Nightmare preyed on.

We know that whatever the Nightmare does in the dream world is enacted in the real world to some extent so Zeztz defeated it in time before the poisoning really took effect.

Though I feel like the main core of the episode was Fujimi's continued efforts to pursue Black Cases, even if no one believes in him but himself (and Nasuka coming around to him) and also solidifying Nem as Baku's dream partner.