Kuromaku (黒幕) is an alias Akio uses for his (crime) consulting service, which available only on the questionable side of the internet.
Using the website, Akio interacts with potential clients who are mostly trolls, as most of them are still doubtful upon the existence of such a service. Nevertheless, he considers each and one of them as a valuable potential client. Akio responds back to them and matches their flow of conversation instead of ignoring, because only by doing so then he eventually manages to change their mind and turns them into actual clients.
It is a consultation done by those who wants or needs to commit a crime but doesn’t quite know how to/what to do. A crime consultant then will construct the lowest-risk and most organized crime plan for them.
There is no limit on what kind of crime that can be consulted to Kuromaku.
So that they can have the least evidence on you, of course? So that the authorities don’t set their eyes and attention on you! And of course, so that your planned crime can be satisfiedly executed.