Monster Hunter doesnt really have a storyline xD
you're basically a hunter and you go out to hunt monsters and carve them for stuff to make better armour and weapons. It takes practice and skill to play it. But once you get the hang of it, it gets easier. You have to memorize the monster's attacks and whatnot and learn to dodge out of the way.
It's a kick ass game and it's really fun to play with other hunters. You can take up to 3 hunters on a quest with you, making it a total of 4 hunters.
In MHFreedom Unite, you get to take felyne comrades with you on your single player quests. The game has talking kitties who stand on two feet. There's five of them you can hire for your kitchen for them to cook for you and also hire felyne comrades to help you hunt monsters.
Good luck, and I hope you get the game. Have fun!