Several men have sex with a prostitute in the first episode. While this is obvious, nothing explicit is shown, it generally shows the men walking away from her while putting on belts.
Women's breasts/torsos are shown several times throughout the show with just the nipples covered. Also, a man who acts as a gigolo is seen in bed with woman who has no shirt on. The nipples are barely covered in these scenes.
There're sexual posters in the main characters' apartment.