Seeing how Kibitsu/Prince seemed to be using her ability while playing the piano, with it being concentrated around her fingers, I'm gonna make the early assumption that her ability increases the effectiveness of whatever she's doing using her fingers. Basically, she's "good with her hands", in more ways than one. Letting her hit the exact piano keys she needs, apply the right amount of pressure, etc. Can easily be used during sex to hit all the sweet spots, and would explain why those girls are so addicted to her without hypnosis or similar being involved.