The plot is that every fictional character made in the history of man are put into a Giant Arena and forced to fight until only one is alive, the character can be from anywhere whether it be an Anime,Manga,Video Games,Movie,Book, TV Series,etc.
http://www.rpnation.com/resources/fandom-smash.2293/
http://www.rpnation.com/resources/fandom-smash.2293/