The Championship consists of a 32-battle elimination tournament (putting it into the player's perspective, it is a typical 5-battle league challenge). Items other than held items cannot be used at all during the battles.
Participants include the eight Gym Leaders previously battled (with the exception of Hinata and Kaito), as well as other trainers that have their own specializations, such as Angelica, who specializes in the Fairy type.
The opponents faced by the player are random save for the championship match. The first two rounds of battle will always be with Goldkorn and Angelica (though not necessarily in that order), and the last two will be with 2 of the 7 gym leaders and Hokage. Just as competitors are randomized each runthrough, so are most of their Pokémons' abilities. After the first battle, the player will fight the characters that were previously seen in the waiting room.
After each battle, the player's Pokémon are fully healed and the player can make minor adjustments to their team to face the proceeding battles.
The Actan will offer to join your party temporarily after defeating it. (You will be prompted to replace one of the Pokemon in your party regardless of how many Pokemon you have, but if you have 5 or less, the Pokemon chosen will not be replaced). Also, it will have Crunch instead of Nuclear Slash but will still have Inferno even though it cannot learn the move. As of the 1.0.1 patch, the nuclear Actan can be caught, but will not be saved in your PC (See Actan's Trivia).
After some dialogue, the battle with Actan is followed by the final encounter with CURIE.
After defeating CURIE for the final time, Theo forfeits the match, leaving the protagonist to claim the championship title.
Urayne will offer to join you in its Alpha form at level 50.
Those looking to shiny/stat hunt Urayne can turn on Autosave set to 5 minutes before battling Gamma Urayne. During a conversation, a flashback of events with Urayne will take place. Waiting 5 minutes before continuing on will trigger an Autosave when the story returns to the present day. Close the game, re-launch it, turn off Autosave, and play from the Autosave. Urayne will appear with its shiny sprite in the nicknaming screen so you don't have to wait until Hall of Fame registration/after the credits. Those looking to check Urayne's stats for ideal IVs and Nature should take the Championship challenge with only 5 Pokemon and not let Actan join them so that Urayne is in the party screen immediately after the credits are done.
If the player has a full party and PC boxes, if prompted by Actan to join the player, the Pokemon whose place is taken by Actan will disappear since there's nowhere for it to go. In addition, because Actan takes up a party slot during the conversation with Urayne, Urayne will not be added to your party and will aslo disappear.