At the End of the Battle

Kai rides King of Knights, Alfred to give Aichi some damage. However, on the next turn, Aichi declares "Final Turn", attacking with Phantom Blaster Dragon and Blaster Dark attacks but Kai successfully guards against both of them. Failing his Final Turn, Aichi is shocked and forced to end his turn, giving Kai the chance to show Aichi what true strength is.

Synopsis excerpt via Kitsu.