Tenchi Masaki, a seventeen-year-old, uncovers a family legend about a sword that sealed a demon within a cave centuries ago. Ignoring the warnings, he releases the demon, a space pirate named Ryouko Hakubi. Their initial clash awakens Tenchi's latent abilities, intriguing Ryouko to stay with him. Soon after, a series of alien women, including the princess Aeka Jurai Masaki, her sister Sasami, the quirky officer Mihoshi Kuramitsu, and the brilliant Washuu Hakubi, gravitate towards Tenchi. As these encounters unfold, Tenchi delves into his heritage, newfound powers, and the cosmic danger on the horizon.