I'm amazed (and amused) at how well he set it up to look like he was some kind of low-life playboy/Casanova.
First he pays for the entire meal (not a lot of money, but thirsty guys usually do it like that to have some kind of "debt" to call in).
Then urgently call her along "to his sisters apartment" (so she shouldn't feel threatened).
Once home, suddenly "his sister" is "out for a while, but don't worry". (Maybe the sister was a bluff)
And once inside, the apartment is really small and there's only one bed. (Sister doesn't seem to exist)
Also the apartment looks pretty trashy, there's trophy underwear spread around, and a pack of opened condoms are blatantly visible. (If she hadn't been stressed out about the possibility that there is no sister, maybe she'd have been more thoughtful about why he was so surprised about how messy it was in the apartment. Of course, a trashy playboy might just have forgotten about it - or his previous "conquest" left it a mess when she left after him that morning...)
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Sure, we know it wasn't so, and if she had actually been a "one-night-girl" looking for that kind of fun he'd probably have gained from the setup. Sadly for him she just wanted a friend (for now at least).