The manga had a man who worked in a business as the protag. Then there was a busty lady who either was part of the company or was a customer; either way, the lady turned his coworkers on him by saying he was doing something perverse to her, then later on she calls him a shitty erect bastard on the train. I believe they also lived together at the end of the chapter. This was all in the first chapter.

Dame Daze... Zen Zen Dame Daze