While both of their titles contain the letter "x" and the word "hunter" in them, the Monster Hunter games and the Hunter x Hunter manga/anime series are pretty different entities. The Hunters of the latter - some of them, anyway - do deal with creatures though, so perhaps that single connection is reason enough for this collaboration between Monster Hunter XX and Hunter x Hunter.
The Hunter x Hunter character who will be appearing as a series of items isn't exactly a Beast Hunter, but he has fought those that fall under that category. He's also the main character, but instead of his typical kid self we get him here in his adult form, which he assumed temporarily to gain tremendous power as well as tremendously long hair that defies gravity.
Without the incredible aura that emanated from him in the manga/anime, that gravity-defying hair looks even more absurd, in a wonderful way. If all you like about him is the hair, you can just choose to equip his head, a.k.a the Gon Head. The other items that make up the Gon Armor series are the Gon Suit, Gon Arms and Gon Legs. Thinking about it, doesn't this mean you're effectively cosplaying as adult Gon in the game?
Anyway, once you're done revelling in the Gon Hair Gon Armor trailer, there's also the opening movie for Monster Hunter XX to enjoy, featuring people in more conventional-looking armour and helmets masking their probably mundane hair.
Monster Hunter XX is the updated version of Monster Hunter X, or Monster Hunter Generations as it is known in the west. It'll release in Japan on March 18 for the Nintendo 3DS, while there's no word of a western release.