In An American Benwolf in London, Kai's grandfather is taken away by the Forever Knights. She escapes and contacts Ben for help. Throughout their adventure to find her grandfather and the legendary sword Excalibur (of which Kai is proven later to be the only one worthy to wield it when she moves it), Ben and Kai exchange some banter. At episode's end, Kai kisses Ben on the cheek, much to his surprise.