1st answer: play the game.
2nd answer: read the blog
...ok I'll concede BF (Battle-fuck) is not defined.
Leaving the history aside, BF, when used properly like here, means orgasm = defeat. Both parties are sexually assertive, and the one who wins the battle gets the upper hand. Sexually. Hence there's no rape in this game.
- If you defeated her she very much does not deny your winner's privilege.
- If you were defeated, well you're the loser and will be treated as such. That's also in your job's description.
- there are also ways to outsmart or be outsmarted without a battle. But you won't know unless you actually try the game.
- there's also romance and out-of-battle events for many girls. Competition ain't all there is in life.
TL,DR: Yes, BF is awesome. I wish other devs and users could use the category properly.