You need to see every single action at least ones. So unlock all actions for desperation/sensitivity and make sure to see all of them.
Stuck too. Can increase Sensitivity * OR * Desperation to max, but when trying to fill the non-maxed bar, the maxed bar drops. Also Ruin is stuck at around 90% (percentage numbers on the bars would be a nice thing to add at some point!). I believe I've seen every action at least once.
There's also no way to exit (presumably until all three bars are maxed?) that I can see.
Replying to myself (always the way - post an ask and the problem goes away!). Had to max out Sensitivity to unlock some actions, allowing Desperation to be maxed, which unlocked other actions. Once all unlocked actions had been done at least once, Ruin maxed out and further actions resulted in things progressing.
Found it for the most part... first fuck her again and again till Sensitivity is maxed out and once more... then there appears a new fuck option. Save the game. You do that and try both. One will have raised "desperation" now.
Then go "masturbate" and "kick her" again and again till desperation is maxed out and once more.
The new fuck option appears again.
After that: spank her pussy and make her cum every time. Now Desperation stays solid and Sensitivity rises again.
Now Desp is maxed, Sens is nearly maxed, but I can't get anything higher anymore.
Normal fuck: "let her cum" rises "Sens" but lowers "desp", "don't let her cum" rises "desp", but lowers "sens". Now take "Let her cum", then go to the poses and there's a new option "degrade". I hope that's it now.
Then regular "fuck" again... Apparently that's it.
No fun... really annoying.