*special thanks goes to Brazil who wrote this episode synopsis
At the beginning of this episode, Sasami comes back from a visit to the family of Tenchi's aunt and their newborn child Taro, behaving a bit odd. Some weeks later, Tenchi suddenly finds himself taking care of Taro (as always, no-one asked him) because his mother became ill.
As it was to be expected, Ryoko and Aeka instantly make the baby an objective in their permanent battle for Tenchi's attention. However, they quickly (and intensively) become acquainted with the less cute aspects of babies. The girls then proceed to demonstrate their incompetence at changing diapers and feeding the baby, while Ryo-ohki gets caught and played with by little Taro, who of course does not know the difference between a plush toy and a live cabbit.
After a while, the girls seem to get some routine with their duties, but they're still overtaxed by the baby's constant demand for care and attention. Unified in exhaustion, they spend the night sleeping on the floor of the living room in order to be able to instantly care for Taro's needs.
So great is their exhaustion that they fail to notice him going on a little exploration trip that takes him to the subspace laboratory where Washu, who is pulling an all-nighter, gets in turn pulled at by Taro. When she sees that Ryoko, Mihoshi and Aeka aren't exactly in top shape, Washu decides to take care of Taro herself. Surprisingly, she is very good at it, and seems to enjoy it tremendously, despite her feigning annoyance.
In the morning, when the girls have recovered, she hands the baby over to them again and returns to the lab, fending off Tenchi's thanks. However, she now seems unable to concentrate on her work and so she returns, just in time to take over from the three girls who are again completely exhausted.
Washu then takes a bath together with Taro at the onsen. As she affectionatly looks at him, a memory from Washu's past emerges, and she recalls another baby and a man, when suddenly her flashback is interrupted by something else "emerging".
The following days are filled with happiness (and a lot of work for Mihoshi, Ryoko and Aeka) as Washu proves to be an excellent substitute mother for Taro. One night Tenchi again thanks her for her help and Washu tells him some things about babies in general, obviously speaking out of experience. After Tenchi is gone Taro calls Washu "mama", which seems to make her very happy and sad at the same time. With a hoarse voice she tells him that she's not his mother.
The next morning, while Washu is happily preparing breakfast for Taro, his parents come to take him back. The sight of Taro's father walking away again evokes the painful memories and Washu tells Tenchi about how she had a child in her youth 20,000 years ago which was taken away from her because the father's family didn't approve of the marriage. With the words "Lineage, social status, why should these things matter so much? That's how grown-ups are. If that's so , I'd be happier as a child, never growing up.", Washu gives a glimpse at the reasons for her self-chosen eternal childhood.
Tenchi is obviously moved deeply by this, but in order not to let the show get too serious, Washu suddenly turns into her (stunningly beautiful and pretty sexy) adult form and tells Tenchi that she would love to bear a child of him. This isn't exactly received well by Ryoko and Aeka, as can be imagined.
The ensueing quarrel is watched by a confused Tenchi, an amused Washu and Sasami who, completely unlike her usual self, seems very serious and lost in deep thought (though it doesn't take 7.5 million years...).