After an adventurous few months in multiple worlds, Kai and the others settle down, eager to show their new friends around the world they love so much. Having defeated evils both at home and across the vast oceans, they are content that their world is finally safe.
However, disaster never seems far away. Two strange figures arrive in the world on the back of a massive dragon, claiming to be in search of the Sanctum's keeper. Before Kai and the others can find out what this means, the world itself begins to collapse. Kwin, ever the defender of her world, mysteriously decides to leave the newcomers alone. Kai guesses she knows more about who they are than she's letting on, but she refuses to tell.
As cities collapse and oceans rise, Kai and his friends are left with no choice but to race the clock and search the entire world for the keeper, a figure they are told can save the world when no else can.
"It hasn’t been without its benefits, however, and this is where you come in. You have become a friend to me like few others have. I’ve met an immense number of pleasant people, but I never expected I would meet one of my best friends here. Through you I also met others, and soon enough I had a whole group of people around me that I loved. I began to realize that the reason I was coming here was no longer for the world, but for you."