I've said the same things to the developers and this is their answer

"The drop rate is quite random. So, this means that you can get a girl really fast, or sometimes you would have to go and battle a bit more!
Don't lose faith, keep on battling!"
"The drop rate is increased and I can reassure you. But never forget there is always the 'luck' chance.
This means you can get girl fast or have to wait a bit and fight."
What do you think? I think they are joking with us.