Misao is the younger brother of Mihoshi Kuramitsu. In the third OVA series Misao had received a letter from Mihoshi, which said that Mihoshi was doing all these things with Tenchi Masaki. Remembering that he once heard that Tenchi is surrounded by women, Misao interpreted that Mihoshi was in a harem and was being abused by Tenchi (the letter was altered by Z originally, and later by Fuku). Because of his concern that Mihoshi would suffer a repeat of what had happened before (which wasn't elaborated in detail), Misao decided he had to kill Tenchi to save his sister.
In order to accomplish this, his grandfather the Grand Marshall Minami Kuramitsu had given Misao command of the Kuramitsu's family's newest ship, the Choubimaru, which had the capability to destroy an entire planet. The plan was lure to Mihoshi and Tenchi to the Choubimaru for a banquet, and to avoid having Mihoshi hate him, Misao would make Tenchi's death look like an accident. Misao would then accidentally destroy the Earth during their fight with Ryoko to avoid the general panic on Earth that the Choubimaru would cause when the Earthlings see the Choubimaru. When Misao had contacted Mihoshi to invite her and Tenchi on the Choubimaru, Mihoshi didn't remember that she had a brother, until Misao displayed one of his old photographs which was when Mihoshi immediately recognized him. Misao then made his invitation, but before Tenchi and Mihoshi could go, Mihoshi had gotten a call from her friend Amane Kaunaq, who wanted to find out Tenchi's intentions on joining the Galaxy Police. Since an interference field was deployed around the Masaki house (deployed to make the capture of Ayeka, Ryoko and Washu easier) made the call a problem, Tenchi and Mihoshi went into Washu's lab so that they could get better reception.
Although Misao was a competent officer, he's insecure and unsure of himself. His is also easily intimidated, as evident when Mashisu Makibi spanked him for calling her a lowly servant. He was also unaware that Mashisu was in love with him. But Misao became aware of this when Mashisu helped snap him back to his senses when he was prepared to go down with the Choubimaru during Ryoko's attack and she had shielded him with her body during an explosion.
It was then Mashisu, who had apparently suffered a fatal injury, reminded Misao that they originally met, when Misao had accidentally hit her with a tennis ball and he admitted that he had apologized for what he did back then, although she was too lovestruck to have heard it and that she was happy to have been introduced to Misao's family. Misao realized that he couldn't forgive himself if Mashisu had died because she was important to him. Luckily, the destroyed section of the Choubimaru, as well as Mashisu's injuries, were an illusion created by Washu on Tsunami-fune, which was borrowed by Seto to show Misao that it is Mashisu and not Mihoshi that he should protect. When Mashisu ran off in embarrassment, Misao was convinced by Noike, Ayeka, Sasami, Washu and Seto to go after her, but Misao accidentally stepped on Mihoshi's face by mistake when he went after her.
After the Choubimaru incident, Misao, along with grandfather Minami and Mashisu, were brought before his great aunt Mikami, and got a punishment of ten years service in one of the family's ventures. Misao accepted his punishment gracefully, but not wanting to be separated from his beloved Mashisu had asked her to marry him. Minami at first objected to this, saying that Mashisu was unworthy, but Misao married her when Misao's mother Mitoto brought the announcement of the family council's support for their wedding, as well as Seto's offer to adopt Mashisu, so that she could be worthy of marrying Misao.
Misao also made an appearance in GXP episodes 23 and 24. By then, Misao's punishment was modified and he became an officer in the Galaxy Army. Misao had also had gained greater confidence in his abilities. After Seina Yamada was accused of stealing the Kamidake II, when he was ordered to turn it over to the Galaxy Army, Misao with his unit had detained his former teacher Amane Kaunaq (Amane had trained Misao and still refers to him as "Rookie"), as well as Kiriko Masaki, Ryoko Balta and Neju Ne Melmas, under the charge that they were accomplices. But unknown to them, Misao was secretly working undercover for Mikami to expose a rogue faction of the G.A. that was aiding the space pirate Tarant Shank, to learn the secret of Fuku, the cabbit that powered the Kamidake II. This showed when Misao allowed the girls to stay in a castle owned by the Kuramitsu family on planet Seniwa that had a computer which they could use to solve the case.
Right after Seina had defeated Tarant, Misao went to report back to his corrupt G.A. superiors, but had actually brought Mikami and an armed escort of G.A. officers to arrest them.
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