Apparently you can snipe kills from your friends battles. Get the killing blow and you get a present! Not a bad way get more rewards, let them do most of the leg work! I'm not sure if the person who found the girl who gets anything...hopefully they do. If not I'm a terrible person! I did do 1 hit throughout a whole fight but not the killing blow and didn't get anything, I'll continue to test this.

-UPDATE-
So actually you do get a reward even if you only hit the girl once not sure if the top contributors get better rewards yet but I did get 10,000 pero just from 1 hit on a girl and I was rank 3 for overall damage! Also I did let someone get the just the killing blow on mine and got a reward of a peronamin N Wild and R Wild. Looks like the best thing to do is to share your girls with your friends so all reap the rewards!