Plot:

The Plot of Pokken Tournament is pretty simple, and that is to fight. If you have never played any of the games apart of the Tekken Series that Pokken Tournament incorporates, then you might find Pokken very similar to Super Smash Bros. Much like the Super Smash Bros Franchise, Pokken has that same one-on-one, fighting type matchups. You even can do special moves and combos, also found in Super Smash Bros.
Outside of the graphics and mechanics, Pokken Tournament is basically about fighting your way up the ladder in a variety of tournaments. Your player will be able to play with a number of Pokemon in order to do this, and will also unlock more and more tournaments and Pokemon as they keep winning. There are also various stages that can be unlocked along the way, as well as different Game Modes to keep the fun going.
There is also a storyline that goes along with playing in the tournaments in Single Player Mode, one that revolves around the mysterious Pokemon Shadow Mewtwo. You will personally journey along for the story with your advisor, Nia, and will battle this mysterious Shadow Mewtwo and their trainer throughout the game mode.