The first page is actually of her laying down with her neck back. So her pose is correct. Just looks crazy because its upright rather then sideways which would make more sense.
That top is skimpy, but it's not like she could wear anything other than a poncho or moomoo. If there is a shirt that could contain her body shape, I've never seen it.
Congratulations for the work done in this manga hentai. It would be cool if someone who understands image editing apply some treatment of these images to improve quality.