Seina Yamada

Seina Yamada is a good friend of Tenchi Masaki and his parents run a small grocery at the beginning of the series. However, aside from Tenchi, Kiriko Masaki and Kiriko's brother Kai, Seina has very few friends; mostly because he has the worst luck in the universe. Minor disasters often occur in his presence, and anyone near him stays a good distance away from him. Seina's usual (lack of) luck almost ends when a spaceship nearly crashlands on his head at the Masaki residence. Its driver, Galaxy Police Detective Second Class Amane Kaunaq, had meant to present Tenchi a pamphlet for joining the G.P., but mistakenly offers Seina the application instead, under the impression that Tenchi was training the boy.

His family persuades him - via forcibly nabbing his signature and thumb print - to fill out the application, with the hope that Seina would win a prize. When he wakes from sleep for the night, he finds himself aboard a spaceship, recruited to be the newest member of the G.P. Academy. He also meets Mitoto Kuramitsu, the ditzy mother of Mihoshi and cleaning lady extraordinaire, before discovering his friend Kiriko is also a GP officer. From there, Seina is thrown into a plan to stop the Daluma pirate guild from taking over the galaxy.

When Seina's bad luck was found to have an effect of attracting space pirates, the G.P. capitalized on it by placing Seina in command of one of the Decoy Fleet's newest ships, the Kamidake (which included systems designed by Tenchi's sister Tennyo Masaki). However, when the ship was irreparably damaged as a result of an encounter with space pirate Tarant Shank, Seto then presented Seina with a ship designed by Washu Hakubi, which was named the Kamidake II by Seina. The ship consist of the main ship body and a cabbit, similar to Ryo-Ohki, named Fuku by Seina. Fuku differs from Ryo-Ohki in that Fuku serves as a terminal body and more importantly, the power source for the ship, thus is not able to transform into a ship. However, according to Washu Hakubi, it is possible for Fuku to turn into a cabbit girl like Ryo-Ohki... if Fuku wishes for it as she matures.

Later, the ship became a hybrid, when under Seto Kamiki Jurai's supervision, it was fused together with Kiriko's second generation royal tree Mizuki (enabling it to generate Light Hawk Wings for protection). The main pod, which house the royal tree in a Juraian Royal Tree ship, was used for the fusion.

During the time Seina commanded the Kamidake and Kamidake II, he was earning an equivalent to a fleet commander's salary. However, because he was still a cadet, that money was kept in a special account until he graduated and was given what he would normally earn. The interest the money accumulated, however, was forwarded to his family on Earth. It was so much money that the Yamada family used it to build a huge new home, as well as building a huge supermarket in place of their small grocery. While Seina was visiting Tenchi back on Earth, Amane, Kiriko, Ryoko Balta, and Neju, who was visiting at the time, worked at the Yamada's supermarket, where they were worked until exhausted.