If you don't want spoilers on how to get the fourth ending (100%) I suggest you stop looking at my comment right about now.
So, I tested this out on Endless mode before trying it out on normal mode, here's the strat, as soon as the game starts, shove both vibrators on Daisy and turn them on (because if you take too long you'll end up with the third ending [75%]) and put on the white and red mask on her. What I think is optional is playing with her boobs whenever a text bubble with a heart appears, example: "... ♥"
That's it! Hope you enjoy your gameplay of this short but well made game!