Sooo... I've got an anatomy question: Is the diamond-shaped extension from her lower garment (serpanty? loin helm? bikini bottomless?) covering a ventral anus anterior to the labia suggested by that crease in the garment, or does she just have a cloaca (as snakes in fact do) under that creased triangle?

P.S. Yes, I may be over-thinking this.
P.P.S. No, you don't have to thank me for the fact you will never again be able to see a naga girl in a manga, anime, or vg without thinking "...Cloaca?". Just doin' my part.

Generally, in anime and manga, lamia/naga have a human ass, which means they have to "sit" on a toilet like a human for number 2, and lean on it for number 1, no matter how stupid that concept may be.

If she were to have a cloacal opening, it would make far more sense for it to be closer to the tip of the tail, anyway, since that's where it is in a real snake. (See post #218202)

Honestly, I would think the most sense would be made with a rectum down at the bottom of the tail as long as one still has a snake-like digestive tract, and the tail isn't just a replacement for legs, while leaving the sexual organs up around human-area, since lamia tend to be portrayed as female-only, and needing human men to procreate. (And therefore, have an evolutionary imperative to have sexual traits that attract human male mates.) (Cassiopeia may be different, though, as she was cursed into her form, rather than being part of a specific species.)

Lamia are ultimately chimera, not actual snakes, so there isn't necessarily a reason for them to be too overtly snake-like. (At least, no more than mermaids have fish-like traits or behaviors.)