Hentai animation

I've seen a few animations that look hand drawn in 2D, but have a kind of depth that makes them seem 3D.  Hard Love Life is one example, where certain parts seem closer to the camera even though they're drawn.  There are other examples that look hand drawn but super detailed, and have smooth but limited animation. 

http://www.mu-soft.com/inside/real/hizashi_complement.htm

this one is superior.