i myself would recommend you to check out these games called "kunoichi sekiren" and "princess reconquista" as thier creators have not only done a great job at the adult part of the game but their games also have some really great and unique mechanics to them (specially kunoichi sekiren).
If you plan to check them out, here are the links to thier ci-en/dlsite pages :
Kunoichi sekiren:
https://ci-en.dlsite.com/creator/17888
Princess reconquista: