When Jack mistakenly destroys a group of scientists' chance to escape Aku, he and the scientists join forces to try and fix the problem, hopefully returning Jack home as well.
When Aku is reborn to set forth his reign of terror, the Emperor's son is sent off to learn the ways of the samurai. That boy becomes a man and attempts to slay Aku with a mighty sword, but Aku banishes him to the future.