I'm pretty certain that is for the lust battle style. They have three styles melee, ranged, and lust. The whip and cum jar are for a lust fighting style.
The cum jar works fine as an HP restoring item in other battles, or outside battles. But in certain battles like the grauls, Bradley, and the angry thing, it triggers an attempt to seduce with zero lust damage and zero healing. It's a bug.
Hmm see, the cums restore your hp and mana but costs high lust and the whip can't be used for melee attack it boosts you lust attack. Try to wear the dragon suite and master underwear and level up your appearance to at least 20. It will help u a lot with lust attack if you like it.
Nono, I can do lust attacks fine. But the cum jar is bugged in certain battles like the angry demon enemy and Bradley's sparring. It doesn't raise HP or Lust, and does a zero damage lust attack. I have high lust attack when using the normal lust attack button.