Yousho is the First Crown Prince of Jurai. His father is the emperor of Jurai, Azusa, and his mother is Funaho, the First Queen of Jurai who is also from Earth. Yousho is the father of Achika and the grandfather of Tenchi.
Since Juraians live a lot longer than people from Earth, it is not known exactly how old Yousho is. However, when he was young (by Juraian standards), he was engaged to his half-sister Aeka, the First Crown Princess of Jurai. Aeka was still very young at the time, even younger than Sasami is now. Yousho did not voice any objection to the marriage, and in fact he seemed to accept it as did young Aeka. However, a little over 700 years from the present, a space pirate named Ryouko attacked the Juraian homeworld. Yousho left Jurai (and Aeka) in order to pursue Ryouko in his ship Funaho. The pursuit led to Earth, and it was on Earth that Yousho defeated Ryouko by absorbing her gems, the source of her powers, into the hilt of his sword Tenchiken. Yousho then imprisoned Ryouko in a cave, and he built the Masaki shrine nearby to ensure Ryouko did not escape. After this victory, however, Yousho did not return to Jurai, but instead decided to live out the rest of his life on Earth. Meanwhile, Aeka waited on Jurai for Yousho's return, but hearing no word from him, left Jurai with Sasami in her ship Ryu-oh to search for him, eventually finding him on Earth.
When Aeka discovers that Tenchi's aged grandfather is her half-brother Yousho, she asks him why he did not return to Jurai. Yousho explained to Aeka that even though the emperor married his mother, who was from Earth, there were those on Jurai who did not want to see someone who was half Juraian/half Earthling to take the throne. Yousho then tells Aeka that he did not want to bring trouble to her by marrying her. He then suggests that she get together with Tenchi.
Although Yousho appears old (he claims that it is because he is away from Jurai), it is revealed later that he does in fact look the exact same as Aeka last remembered him on Jurai. He keeps the disguise since he is still afraid of marrying Aeka and also to not draw suspicion from people around him as to why he is not aging. He only dropped his disguise on the request of his mother when she came to visit him and everyone else in OAV#13. Yousho tells her mother that there is a possibility that Ryouko's gems are probably keeping his tree Funaho and himself alive.
Yousho is very powerful, as he demonstrates in his fight with Kagato. He is an excellent swordsman who handles the sword Tenchiken with skill that comes through years of experience. He also has the ability to call forth shields which, are actually weakened versions of the Light Hawk Wings created with the help of his Tree Funaho, to deflect the blows of his enemies. In addition to his swordsmanship, Yousho appears to understand how to use various martial arts as well.
Yousho spends most of his time at the shrine, though on occasion he drops by the house, especially now that it is conveniently located at the bottom of the shrine steps, courtesy of Aeka. He is usually quiet, but that silence belies a wealth of knowledge that has come through experience. He also knows more about what goes on in the lives of Tenchi and the girls than he lets on. He constantly trains Tenchi in the art of sword fighting, and at the same time he loves to tease Tenchi as well. He gets along well with everyone, and everyone within Tenchi's extended shows him respect, even Ryouko, especially now that it is known that she was not acting of her own free will when she attacked Jurai, but rather she was under the influence of a person named Kagato. One thing he does love to do is play matchmaker with Tenchi and the girls that live with him.