Tenchi manages to get the keys to the cave his grandpa told him not to enter because it contained a demon. Curious Tenchi enters the cave and accidentally frees the demon. The next day in school, Tenchi sleeps into the night where he is confronted by the demon who is an attractive woman named Ryoko. She decides to take out her 700-year frustrations on Tenchi by attacking him. This results in most of the school being destroyed until the sword Tenchi got from the cave activates itself and cuts off Ryoko's hand. After regenerating her hand, Ryoko vanishes. When Tenchi gets up in his bedroom, he finds Ryoko sleeping in his bed to his surprise.