Good concept.
Would be nice to have more interactivity with the world. Things like replying to the messages, having a different camera angle for sex scenes, etc. There was a message asking for a video call in the game, could be a masturbation scene? Would also be nice to have proper endings for both outcomes.
As others have mentioned, it would also be nice to have the ability to take on multiple colleagues at the same time.
Also, as for the idea about replying to messages, it would be great to get different reactions from different colleagues. If you chose a response that the colleague did not like, he may be rougher (and maybe take longer) with you. It could also serve to extend the gameplay a bit, so you can have multiple days, where over the days you will have to learn each colleague's preference and choose the best reply in order to finish the last days. With some colleagues, you can tell them to come back later, but some won't like that and come anyway and be rougher as mentioned before. The report could progress over the course of, say five days, instead of having one report each day (either works but honestly I'd say I prefer the first one) .