Spaceship Agga Ruter (スペース・オフェラ アッガ・ルター) is a 4-episode hentai OVA released by AIC in September 1998 to April 1999. The story is set in the same universe as Tenchi Muyo! Ryo-Ohki. An 18+ rated game titled Spaceship Agga Ruter: The Terrible Space Witch (Space Ofera アッガ・ルター 恐怖の宇宙魔女) was released for PC on April 15, 1999, with the story occurring a year after the original anime.
The story is about the guardian android of her spaceship; Agga Ruter, named Kei, and an orphan boy named Taiyo, who she had raised and adopted, as they travel through space together. Until Taiyo's age into maturity of 21, Kei taught Taiyo a number of very special lessons regarding how to please and pleasure women, which mainly meant making love.
By the time Taiyo was old enough to have a fulfilling and pleasurable relationship, he and Kei start on their new adventure seeking to find the Virginia and other key components which her master has sent Kei to seek out. Along the way however, space pirates including Jannis, are hot on their trail to claim the ship and the other secret components for themselves.
- This series probably takes place at some point between Yosho arriving on Earth and the beginning of the Tenchi Muyo OVA. Possibly much earlier. Kei is actually a less sophisticated version of Zero. The antagonists are the Shank Pirates, ancestors of Tarant Shank, at a period before the Daruma Guild united the different smaller pirate groups and they were much more powerful. Their interactions with Taiyo precipitate their losing power in the galaxy.
- It is rumored that one of the characters from Agga Ruter appears in the main Tenchi series, though the identity of this character has yet to be revealed.