The bit that might be getting you may be the 'yes' choices. Choosing the "Yes" (in bold if that is too difficult to see) might be the most confusing one; it's when he's offering his 'help.' He also appears to like it if you request him to punish you. And, of course, when you go with the 'this was pleasurable' choices whenever they pop up. It gets to the point where your character instinctively says 'yes' to him; I believe that is the signifier you have reached his 'good' ending.
Basically? Be obedient, eager, and a masochist.