Irma and Milli - The UNDER COVERs

Irma Asta and Milliam Duffoner are the most famous partners in the notorious 2nd division.
All the things they do are over-the-top.
They are currently working on the serial case involving missing women.
However, they couldn't embark on the investigation of the suspected organization named Onzereau, which is one of the biggest criminal organizations in Europe.
They decided to penetrate their stronghold called "Guest Palace" to clean their tarnished reputation and solve the case.
However, what they found in the establishment was scenes of a very filthy sex-related business...

Can they resolve the case?
And also, can they make their way out of the Guest Palace safely!?

[From DLsite English]