Chikan Shita Joshi*sei to Sonogo, Musabori Au Youna Doero Junai

Chikan Shita Joshi*sei To Sonogo is much more vanilla and there's only one girl, but at least in the first minutes there's the groping in a train part that the title says about, and that's exactly what Manin Densha also has by lots and by indication of the title too, there's also some of that rapey aspect in both, but as I said Chikan Shita is much more sweet, take it as you may. 

This may seem like a bizarre recommendation, but both of these anime are examples of how CG can be done right. Houseki no Kuni, aka. Land of the Lustrous uses its 3D CG as a way of highlighting the crystalline aspect of the characters. Thus the CG becomes a piece of the character itself. Chikan Shita is a hentai that uses its CG alongside 2D elements to present more fluid sex-dynamics in Doujinshi based adaptation without going so far as losing the entirety of a comic style. This allows the animation to far transcend the wiggling still frames that Queen Bee hentai is known for.