This was before Fakku transformed to being almost exclusively paid subscription content. I'm not sure if this series is on Fakku anymore. I read it probably around 2013-2015, though I loved exploring Fakku deeper, so it may be from before that even. I remember it was a series, and had quite a few chapters, probably 11 or even more. Pretty sure the characters were original, i.e. not doujin. The setting eludes me, but I think most of the characters knew each other through work - some sort of business, maybe manga publishing. Female character with long dark hair was very popular and I remember the comment section being mostly praise for her. The one scene I recall clearly is her eavesdropping on a guy having sex with another girl and masturbating to it. That other girl said something about this long dark haired girl, and called her old (oba-san or something), to her chagrin, and she commented she isn't even thirty.
If anyone can help me hunt this down, much appreciated. It's been driving me crazy.