At first glance, I thought it was missing the torso and she'd been beheaded, as if ripped to pieces by the tentacles, and the various oozes were blood.
Thighs are too narrow, shins are a bit wide. Torso's too small, mainly horizontally but also a bit vertically I think. Arms seem a little short too. Head's a bit big in proportion... and I feel the eyes are located a bit too high on the face.
The curviness, in general, is good. She's a bit lacking in the hip region (and the stomach above it), but she's got good definition in the aforementioned shins, and I feel the shoulder and bust regions have good detailing in them.
Maybe try drawing your person bigger? You've got the room on that pad.
That head on the left is totally unnecessary, and utterly detracts from the femininity of the drawing.
I'd say her thighs are a bit too skinny and short - and the knees too big and detailed. The shading's also very heavy.
I think the bigger size of the drawing helped you to keep proportions consistent. Maybe consider getting a harder pencil? H or 2H? It'll let you draw finer, lighter lines with the same force of hand.
Take 2:
This time I tried combining the Manga style I'm going for as well as the realistic one from the previous pic. I also took some suggestions from readers and tried "curving her out" more.
Please excuse the blurriness I can't afford a scanner and it is just a rough draft.
Also I kind of wanted the Japanese middle aged woman house wife bun and hair catcher hairdo.
UPDATE!
This is more ecchi then hentai, but I was checking out some WIP movies the other day and was inspired by a scene of a chick getting deloused and forced to shower in front of a guard. :3
Again not the best quality, as it was again taken with a phone cam since I dont have a scanner. Also a fully dressed MILF'ish woman I drew from boredom. The first is colored the second is black and white.
some crappy sketches. Just for practice. The first one is a reclining position, the other two/three were meant to be rough sketches trying to get the ass up head down position. X3