where the male MC is being forced to sodomize (he isn't conscious) the female MC (it's mature/ecchi so nothing explicit is really shown except nipples) while the villainess masturbate while watching.

In a later scene, we see the female MC standing up at dinner and she complain her bottom hurt too much to sit down.

I remember the female MC wearing spats and maybe having twin tails, but I'm not certain about the latter.

I tried searching for hours with no luck so I'm asking you guys, if anyone have an idea. 😁

Found it, it was https://www.mangaupdates.com/series/kh83t82/shishunki-na-adam-evil-eyes

I was searching for shonen but it was under seinen