Pikmin 2.5 is the sequel pikmin 2 and all the characters have different storys (it's like sonic adventure dx)
Olimar Louie and Seth head to the pikmin planet but crash landed on the pikmin planet and died and apper in the "pikmin nether" a place where dead pikmin go (yes it's he*l) the reason why they are there is for all the pikmin they killed in they're jouneys so they get out with help of the pikmin to defeat the devil
The prestiant's story
After you beat olimars louies or seths story you get a cutscene of seth noticeing that they left louie at the pikmin planet and both olimar and seth belive he's dead from the big explotion the devil made when they defeated him they come back and to tell the pristiant and since the prestinat has to give the news to Louies family he takes olimars ship and goes to get Louie.
There is 4 player multiplayer and all four characters have the same pikmin Red for Olimar Blue for Louie Yellow for Seth and Purple for the Pristiant. you choose a challenge then play