Jack meets girl, girl is Aku's daughter, they fall in love, Jack loses sword, Aku plans to publicly execute Jack, Aku turns his daughter evil, the power of love breaks Aku's hold on daughter, Aku's daughter grabs sword and transports herself and Jack back in time to the first episode.
Jack absolutely bodies Aku, Jack and Aku's daughter are about to get married, Aku's daughter poofs out of existence, Jack sees a ladybug and smiles.