I searched for quite a while before asking this and didn't find anything. What happens? Do they become the Champion? Do you just black out and go to a Pokemon Center? Do they have to battle Hau/Kukui/someone else to become the Champion? Does nothing happen?
You simply black out and go to a Pokemon Center. If you return to the League, the game acts like the battle never happened and you remain the Champion.
Hope I helped!
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