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.
Before the events in the OVA series, there was the crown prince Katsuhito Masaki. He spends some time at the Science Academy where he meets a young Airi before an attack on his home planet disrupts a planned marriage to Princess Ayeka.
This sequel to the 1997 novel condenses numerous OVA 3 and Tenchi Muyo! GXP anime plot points into a larger epic arc. While the previous volume focused primarily on the emperor Azusa, this edition looks at the upbringing of his 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.