PvP feels terrible.
1) It is not interesting or engaging.
There is nothing special about the art vibrations and the system to determine damage, defense, ego, etc is arcane and seems arbitrary. This is also true with boss battles, to be honest. So I imagine most players just skip the "animation" of most fights. I suppose you can only ask so much from a simple game such as this, but the other points really spell out or exacerbate why this is a problem.
2) There is no way to noticeably/reliably adjust the odds (or even consistently calculate them).
Epic boosters (which are usually only ever acquired through the PvP system, it seems) seem to make little difference. Even so, buying boosters cost Kobans and using Kobans for anything that has no chance of rewarding girls seems rash. Even if they do function well, there is no way to measure or gauge how well boosters work. Then, you often just randomly lose to people with much worse stats (and occasionally win against those with significantly better stats, though that seems less common).
3) The rewards are meager.
Mojo was only interesting as a meter to see how persistent players were at the PvP system. Even then, before we started losing it, I was constantly being offered opponents that present 0-1 Mojo. The amount of money per fight is negligible considering how much you make with 10+ girls. The other rewards are rarely anything of actual value worth pursuing (usually common and uncommon crap to sell for less money than the small amount of money gained from the money rewards). The experience isn't enough to even tickle the meter and who knows if it is still bugged.
4) Extra fights (gained through the Tower) to challenge specific players still use Combativity and give the same weak rewards.
This is self-explanatory.
5) The penalties for losing the fights you are stuck with seems strangely punishing for a game that wants people to engage with the mechanic.
I mean, why play if you don't get any real entertainment or competitive value out of the system?
That said, the bonuses for winning enough in a day seem like a step in the right direction, even though getting a common equipment piece for winning a few fights is pointless. The experience and money rewards here might be enough if everything else is fixed. Extra combativity is nice, if somewhat light.
Also, why did refills go up in cost?