To date, there are three volumes in the True Tenchi Muyo! series of light novels. Volume 2 "Yosho" was written to introduce additional characters relevant to the OVA episodes that could not be squeezed into the limited runtime of the existing seasons.
Princess Ayeka is to be wed to her half-brother, Yosho (Katsuhito Masaki), when suddenly the Planet Jurai is under siege and the groom disappears fending off the perpetrator Ryoko. In what originally took flashback form during the OVA episode 3, now Tenchi fans can discover much more about the affable Yosho, from his tutelage by Seto to befriending a young Airi at the illustrous Science Academy and much more.
This sequel to the 1997 novel helps connect OVA and Tenchi Muyo! GXP series plot points into a cohesive whole. While the previous volume focused primarily on the emperor Azusa, Volume 2 focuses on his direct heir.
For more information see Continuities.
Tears flowing down her cheeks flushed with embarrassment and mortification, Airi was wracked with sobs. More than being shown the difference in their stature, her heart was full of the feeling that she would never be able to see Yosho again. Airi fled the building. 
- True Tenchi Muyo! vol.2 (Light Novel) © Yousuke Kuroda & Masaki Kajishima 1997. Afterword.
- Kuroda and Kajishima, 1998. Page 145.