In chapter 10, Dahlia overheard fake zena and vouivre munching on a poor crewmember. In chapter 11, you can see dahlia telling ash and orhan something, which I assume to be what she heard.
Some theorizing here, you think Kensuke was also transformed into something, which is why it could open the door?
We've established that Kensuke is a mollusk-like thing and that another mollusk-thing, the Nightmare/Shin is related to dragons, maybe Kensuke is also dragon-like now?