Sushi bar?
Where on the Castle do they raise sushi?
In Habitat B. A lot of the folks who took up residence there brought some of their tastes with them, and some of the critters.
Habitats A and B are somewhat like giant cruise ships, except adapted for space. They have multiple decks, and are powered by fission nuclear reactors for growing crops, fish farms, aquarium critters such as octopi, and so forth.
It's also the most crowded, well-earning its nickname, "He's Touching Me!"