Misao is Mihoshi's younger brother, and he first shows up trying to kill Tenchi—though not for the reason you'd expect. In the third OVA, Misao got a letter from Mihoshi describing all her adventures with Tenchi, but because someone had tampered with it (Z at first, then Fuku), he completely misread the situation and convinced himself Tenchi was abusing his sister in some kind of harem setup. Wanting to protect her from repeating past trauma, he decided murder was the answer.
His grandfather, Grand Marshall Minami Kuramitsu, gave him command of the Choubimaru—a state-of-the-art family warship capable of destroying an entire planet—and Misao's plan was to lure Tenchi and Mihoshi aboard for a banquet, kill Tenchi while making it look accidental, and then destroy Earth to cover it up. When he called Mihoshi to invite her over, she didn't even remember having a brother until he showed her an old photo. Before they could board the ship, though, Mihoshi got a call from Amane Kaunaq asking about Tenchi's Galaxy Police status, and the interference field around the Masaki house forced them to head into Washu's lab for better reception—which threw off his whole timeline.
Despite being a competent officer, Misao's genuinely insecure and easily rattled. Case in point: he got spanked by Mashisu Makibi for calling her a servant. He had no idea she was into him until things went sideways during Ryoko's attack on the Choubimaru. When Mashisu shielded him from an explosion and seemed fatally injured, something clicked—he realized she actually mattered to him. Turns out the destruction and her injuries were all an illusion cooked up by Washu to make Misao see that Mashisu, not Mihoshi, was who he needed to be protecting. After some gentle peer pressure from basically everyone around him, Misao chased after her (and accidentally stepped on Mihoshi's face in the process).
The whole debacle landed Misao, his grandfather, and Mashisu in front of his great-aunt Mikami, who sentenced them to ten years of service in a family venture. But Misao wasn't about to let Mashisu go—he proposed on the spot. His grandfather initially shot it down, saying Mashisu wasn't good enough, but Misao's mother Mitoto showed up with news that the family council approved the wedding and Seto was willing to adopt Mashisu to make her a suitable match.
Later, in GXP episodes 23-24, Misao's punishment got reworked and he became an officer in the Galaxy Army. By then he'd gotten a lot more confident. When Seina Yamada got accused of stealing the Kamidake II, Misao and his unit detained Amane Kaunaq (his old teacher), Kiriko Masaki, Ryoko Balta, and Neju Ne Melmas as accomplices. What nobody knew was that Misao was actually working undercover for Mikami to bust a corrupt faction within the G.A. that was helping the pirate Tarant Shank and trying to learn the secrets of Fuku, the cabbit powering the ship. That's why he quietly let the girls use a Kuramitsu family castle on planet Seniwa to investigate. After Seina took down Tarant, Misao reported back to his crooked superiors—except he'd brought Mikami and armed G.A. officers with him to make arrests.
Content compiled by AnimeList.moe from publicly available sources.
