Yosho was the only child of Jurai King Azusa and an earthling descendent of Masaki: Funaho. Because of his mixed heritage, his life was complicated to say the least.
Because of her mostly human heritage, Funaho was under a lot of heat from Jurai Royal Family. Thanks to Misaki, Funaho have managed to gain a support of Masaki and Kamiki clans. This by itself was quite remarkable, considering the fact that very few queens were ever able to gain the support of two clans at once. However, the Amaki clan- a family who held a grudge on Masaki clan ever since Azusa came to power, still remained strong. The remaining family- Tatsuki clan, chose to remain neutral.
Because on this annoying situation, Yosho had to learn to be very careful about what he says and does at the very young age. He was facing a lot of pressure do to the fact that he was one of the two only realistic candidates for Jurai throne. If he loses necessary support from Jurai Royal Family, the throne would go to Syuuzen Amaki, an evil man who, though pardoned for his crimes, is always up to no good.
And as if things weren't bad enough, Yosho had to deal with Misaki's, who had a crush on him [long story]. As the result of all this stress, Yosho became a sardonic, bitter person. Thanks to Funaho, he was a fairly open person, harboring no prejudices whatsoever. At the same time, Yousho has gone through intensive martial arts training. he have become fairly strong, even for a Jurain. The only person who could realistically challenge him was Misaki.
When Yosho was eight, he was bonded to a first-generation tree. It was fairly young compared to the other 1st generation trees, but it's power rivaled Tsunami. Plus, it was packed with exotic but powerful weapons. According to a tradition, each new partner gives the tree a new name. Yosho chose to call it Funaho.
Around the same time, Yosho's half-sister, Ayeka, was born. Four years later, they were officially arrange to be married as soon as Ayeka was old enough. Yosho was not to happy with the idea because he only thought of Ayeka as a sister. Meanwhile, Ayeka couldn't be happier. She went as far as genetically altering her hair to fit Yosho's idea of a perfect woman. Only a few weeks later, Yosho faced another shocker- his grandmother, an all-powerful Seto, has arranged for him to attend the Galaxy Academy.
He arrived there shortly afterwards, with Funaho disguised as an ordinary training vessel. At the spaceport, he was greeted by Airi Magma of the Airai Royal Family. She was two years older then him. Airi was suppose to be Yosho's senior, which basically means that she was responsible for taking care of Yosho during his stay. As time went on, their friendship evolved into a passionate, Romeo-and-Juliet-style affair.
This went on for several years. Yosho would stay on Jurai for half a year, and spend the rest of the time in the Academy. All was good until Airi found out that she was arranged to marry on of the Amaki men. Like Yosho, she had no choice in the matter.
Airi tried to talk to Seto(who just happened to be stopping by) to see if she can do anything about it. Seto, who had the best network of informants in the Galaxy at her disposal, knew about the affair. She offered her condolences, but explained that she was powerless to help, since Jurai and Airai were not at their best terms at the time. Poor Airi was devastated. Still, the couple decided to try and make the best of the situation.
Few weeks later, it was time for Yosho to return to Jurai for another half-a-year. The couple bid each other farewell, not knowing if they'll ever meet again.
However, just when Funaho was exiting Galaxy Academy space, he received an SOS from the Jurai fleet. The impossible was unfolding- the Jurai Defense Fleet was literally massacred by one lone ship. Alarmed, Yosho rushed to Jurai at the top speed.
It took him five hours to get there. By that time, the entire Defense Fleet was completely obliterated. Ayeka's ship, Ryo-oh, was disabled, leaving her in the mercy of Ryo-ohki and her pilot- Ryoko. Just when Ayeka thought it was all over, Funaho descended from the atmosphere, attacking Ryo-ohki. Yosho beamed down and tended to a shocked Ayeka. Seeing it as an opportunity, Ryoko abandoned her ship and ran to the palace.
Once it became clear that Ayeka was in no immediate danger, Yosho ran after Ryoko. He found her in the Royal Tree chamber, looking like she have just seen a ghost. As soon as she saw Yosho, she came out of the shocked sate and ran away at the top speed. Yousho went after her. It is fairly reasonable to assume that Yosho decided to use it as an opportunity to "vanish", thus allowing him to return to Airi.
However, something happened that neither Yosho or Ryoko could possibly predict. As the chase went on, Ryo-ohki headed toward an primitive planet simply known Earth. in the battle, Funaho managed to cripple Ryo-ohki, sending it crashing into what is now a lake. Meanwhile, on the ground, Ryoko was not doing to well. desperate, she took a local priestess as a hostage. Her name was Kamiki Masaki, and she was actually Yosho's cousin. Yosho managed to rescue Kasumi. He then stripped Ryoko of her gems using the Master Key and imprisoned her in a cave. He then decided to stay on Earth for good. He married Kasumi, thus becoming a priest of (duh!) Masaki Shrine.
The tree later grew into the Masaki tree and can be seen in many episodes. Once a Jurain tree roots itself in soil it cannot be used as a spaceship anymore. Although it cannot fly, his tree has kept him young ever since. His appearance has been altered by Tsunami, but its only a disguise. She did that because I think it'd be a little weird that the old man who lives in the mountains never seems to age. He can cancel the illusion at will. Yosho met a young girl with whom he fell in love with. Note: Tenchi's grandmother in OAV episode 5 when Tenchi was growing up was his paternal grandmother. He married her and took on the name Katsuhito Masaki. Through her he inherited the Masaki shrine.
Although he took several wives during the 700 years that he spent on Earth, Katsuhito and his wife Itsuki only had one child. Her name was Achika. Achika's mother died when she was young. Yosho began to train Achika in swordplay so that she could return to Jurai in his place. However, Achika rejected her father's vision for her future in order to live a normal girl's life.
After Achika's desire not to ascend the throne Yosho waited 13 years. Then Tenchi was born he trained him as he did Achika and Tenchi proved to be a better Jurian knight than he was. Although Yosho has all this power, he does not interfere with Tenchi's life. Many times he could use his power so that Tenchi wouldn't have to but, if he did Tenchi would never gain the confidence and experience he needs.
Yosho's sword also called Tenchi or Tenchiken, is the master key. Whenever a spaceship tree accepts a new owner they are given a part if its branch as a control device. The device is shaped to suit its new owner. Ayeka's is the tiara she wears on her head, Sasami's is a trigger looking thing, and Yosho's is a sword. Because of Funaho was a first Generation tree the control device can operate any spaceship tree of equal or lower generation. The Master key can even override a spaceship tree's control device. An example of this happening is when Ayeka was prevented from controlling her ship in OAV 2 and Ryoko smashed it into the Earth.
The sword also houses Ryoko's gems. During Yosho's battle with Ryoko he removed the gems and placed them in the hilt of the sword. Ryoko has managed to recover one of the gems when Tenchi gave it back in OAV 2.
During the TV series, the sword had a more minor role in the story. The sword wan only capable of channeling one's Jurai power and creating a lightsaber.