Tenchi Muyo!

Tenchi Muyo is an manga and anime series metaverse currently spanning at least 4 OVAs, 3 television series, 3 movies, several other spin-offs as well as radio plays, Pen-and-Paper Games and Videogames.

It's about an Eathling-Alien hybird high scool boy who encounters many strange alien & monster girls who eventually end up living in his house, competing for his love...

Episode 4
Almost the entire fourth episode of the first OVA consists of nothing but the main cast relaxing in the hot springs. Ryoko mocks Ayeka by pulling off her towel, so Tenchi gets to see her naked. Ryoko and Ayeka start arguing about Tenchi's affection, getting Ryoko so enraged that she summons a water demon, all of this while completely naked, no less. Because Ryoko didn't bring her power gems she's unable to keep control of the beast, so hilarity ensues while the gang has to fight against the demon, leading to some collateral damage.

Episode 5
The next episode starts right with Ryoko sitting in the onsen again (or still?) and drinking sake. Ayeka joins the party and gets bright red from drinking.

Unknown Episodes
Another episode shows Washuu (Ryoko's mother/ceator) having a bath in her own floating onsen alongside Tenchi's baby cousin. The boy takes a dump in the water, causing Washuu to drain all the water and clan up the mess.

In yet another bathing scene she was able to tell an impostor Ryoko by recognizing the trademark of the evil scientist who created her on her butt.

Tenchi Muyo! in Love
Kiyone Makibi is shown bathing in a Barrel but then is transported out of the barrel naked by Washu.



Tenchi Muyo! Daughter of Darkness
In the second movie, Mayuka, Tenchi's mysterious "daughter" from the future, surprises him while sitting in the onsen.