Damnit, I knew I shouldn't have trusted that bloody brit. Now she gone and stole all our military secrets.

She's suppose to be a combination of

Too much 2-4-11 turned her into like that =w=

So naka's hair buns and Agano's everything else it seems

Despite being the oni of her class, she has a less humanoid figure than the Tsu-class. Although at least, she has a fully-visible humanoid head.

that's because she's modeled after the fate of one of 2 ships that were lost at Truk that she takes her design from.

Naka was blown in half before she sunk so that's why she's legless.