When I first read this, my immediate reaction was: 'What? That's it? But this ended so abruptly! Why? There could have been so much more to it! It could have developed into a love story!', etc. I thought about it, then realised that this is exactly how the slave feels. He even says: 'that's so sudden'. So I'm guessing that it was deliberate on the mangaka's part, in order to make us truly empathise with the slave at that moment.
Btw, note to self: You should really take this as a warning not to fall for Doms who don't care. Learn to differentiate when they're PLAYING cruel, and when they're just being jerks!
The Master and Me