I am looking for a series I believe I started some time around 2006-2008. It was most likely on OneManga since that’s the only site I remember using during that time.

I remember a guy going to see a fat yakuza or mobster in what seemed like a basement under his host club or something similar. The yakuza was sitting in a chair with various girls around him as well as some of his underlings. The two scenes I distinctly remember are the one from above and then another where one of the boss’s girls turned away to say or do something and the boss shoved his finger up her skirt and inside her. He then kept them there while having the conversation with the MC.
I’m 98% positive that it wasn’t an H-manga. More along the lines of a seinen type.

No idea what it might be but maybe this helps:
Yakuza/s+seinen+ at least 1 Release
https://www.mangaupdates.com/series.html?category=Yakuza%2Fs&genre=Seinen&filters%5B0%5D=some_releases&perpage=50

It's only 2 pages - so maybe you get lucky