The mysterious warrior summoned by D3 and Tokimi is sent to Earth. Meanwhile, Tenchi reminisces about the unusual events in his life that have led him to where he is now, as well as the death of his mother ten years previously. Ryo-Ohki wanders off and gets lost in the woods. After coming to her rescue, Ryoko begins to act more affectionately towards her. The next day, the Masaki household receives a most unexpected visitor.

The woman who arrived at the Masaki house turns out to be Tenchi's sister, Tennyo. She has arrived with news that Seto Kamiki, the princesses' grandmother and self-appointed matchmaker of the Juraian royal family, has picked out a fiancée for Tenchi. Before long, Tenchi's grandmother Airi arrives...but what has become of the would-be fiancée Airi was escorting?

A combination of stress and exhaustion leaves Tenchi bedridden, and Tenchi's fiancée Noike nurses him back to health. Once he recovers, Noike shows Tenchi a new experimental Juraian ship designed to be more effective against any attacking foe. Meanwhile, the Kuramitsu family have received word that Mihoshi is unhappy on Earth, and send their state-of-the-art battleship out to collect her.

Mihoshi's brother Misao develops the notion that his beloved sister is part of a harem run by Tenchi and swears to kill him. However, his adjutant, Mashisu, has other plans for the mission. Meanwhile, the princesses' grandmother, Lady Seto, arrives for a visit, and the family prepare a special meal to welcome her.

The girls fight off Mashisu and her heavy mob, and Ryoko and Ryo-Ohki take on the massive battleship the Chobimaru. Mashisu, meanwhile, is forced to confront her feelings for Misao, and she begs Misao to make a choice between her and his beloved sister.

Lady Tokimi's progeny Z finally moves against Tenchi, and an epic battle in space ensues. However, when the other two chōshin, Tsunami and Washu, discover Z's motivation for wanting to kill Tenchi, they are forced to move against their sister, bringing about a confrontation that threatens to destroy Tenchi, Z and the universe itself.