Tenchi and the girls are charged with the duty of looking after his baby cousin, Taro, for a few days. As can be expected, chaos ensues and before too long the girls have run themselves ragged. It takes Washu to show them how to care for a baby, but even under her instruction they cannot cope, so Washu takes on the job single-handedly.

Ryoko accidentally damages a robe that belonged to Tenchi's late mother. When Tenchi yells at her, he accidentally upsets Ryo-Ohki as well. The heartbroken Ryo-Ohki sulks in Washu's laboratory, where her emotions affect a colony of shape-shifting creatures (the same creatures used as a base for Ryoko and Ryo-Ohki), causing them to break out of the lab and make a beeline for Tenchi.

The dastardly Dr. Clay, acting on the orders of the mysterious Lady Tokimi, sends his robotic slave Zero down to earth to capture Washu.

Zero fails in her mission to capture Washu and returns to Dr. Clay. Tenchi, Ryoko and Washu pursue her to locate and rescue the real Ryoko. When Washu confronts Dr. Clay, she reveals that she and Clay were once contenders for the director's chair at the Science Academy, but Clay was cast out for misusing his scientific talents. He tries to destroy Tenchi as a means of manipulating Washu, but Zero betrays him and he is forced to destroy his ship to make an escape.

Tenchi's life is disrupted once again when some visitors from Jurai arrive. Funaho, Tenchi's Juraian great-grandmother, and her sister Misaki, who is also Ayeka and Sasami's mother, are paying a visit to Earth. Funaho has come to see her son Yosho, and to make an interesting offer to Washu. Soon after, Misaki and Funaho's husband, King Azusa of Jurai, arrives and tells Ayeka that she must marry the man he has chosen already, Seiryo.