It could be someone completely new, a character created just for this fanfic. Maybe he's a normal villager who has a kind heart and fell in love with Sakura when he saw her helping people in the village. He doesn't have any ninja powers but he has a great sense of humor and that's what attracted Sakura to him.
It could be Hinata. In the original series, Hinata has a deep affection for Naruto. In a fanfiction, it would be a natural progression for her to be his secret fiance. Maybe they got engaged secretly to avoid some political unrest in the village.
Well, the Predator in the game is an extraterrestrial hunter. It's from a species that values combat and the hunt. They travel across the galaxy looking for the toughest opponents. In the game, when they encounter Aliens, it's a battle of two very different but equally deadly species. The Predator's story is about proving its worth as a hunter, using its advanced weaponry and stealth abilities to take on the Alien hordes and sometimes even humans who get in the way.
Predator and Alien were classic sci-fi novels as follows:
1 Predator (Warrior Series): Written by William gibson, it includes Predator, Alien: Contract, and Alien: Origins.
2 Alien (Alien series): Written by Ridley Scott, it includes Alien, Alien 2, and Alien 3.
I hope you like these novels.
It could be a new and powerful dark wizard. Someone who has mastered dark magic to an extent that makes them a huge threat to everyone in the wizarding world, like a more menacing version of Voldemort.