To date, there are seventeen volumes in the True Tenchi Muyo! GXP series of light novels. Volume 15 was written by Masaki Kajishima, and has yet to be published outside of the main readership in Japan.
Volume 15 is the first volume in the series that doesn't cover any of the material used in the anime series,
In a flash-forward chapter, we meet Airen Kariyuuku Kaou, sister of Souren, a Kaou Princess (low in succession) and a Renza Military Officer, the head of maintenance, specializing in the Knight Calvary, on the single spaceport on Barrium. The spaceport is, depressingly, in the middle of an arid desert, the only way to operate technology on an otherwise magical planet. She meets an interesting young cadet training to be a knight pilot. Multiple things go wrong with his Weak Knight, it seems the cadet has a serious problem with bad luck, and he is is forced to pilot it manually. She notices in his first run that he seems to be faking being a beginner pilot- he obviously has skills. In a month or so, the cadet has risen through the training and he is in a practice battle with others when Space Pirates come to raid the spaceport. The cadet, in his barely armed lowest class Weak Knight, single handedly takes out several Earthly Knights and even a mid-class Aquius Knight. Airen realizes that she has fallen in love with the cadet.
Seina's captors are able to evade detection from a handful of Seto's personal scouts as the Racepshi continues through hyperspace for Renza space. Airi informs him over a connection that she cannot do anything about it. All she can do is warn him to be on his best diplomatic behavior in light of the confusion with the Renza gang. It is unclear to Seina that most of the Kamidake crew have also docked.
Airi then suggests he get drunk while he still can. Mikami takes over the conversation for her. She decides to rephrase his kidnapping as a special dispatch mission to avoid unwanted media attention. The Kamidake has to remain out of the public eye as well.
Seto joins the call to say the scouts have had their pay cut for their incompetence, and before long points out the traitor standing him before ending the call.
Seina is reacquainted with fellow ship stowaway Kuisu. She has him cornered in the guest room. Seina bemoans that the concept of borders, whether political or interpersonal, are constantly changing for him. Nevertheless, he does notice that compared to Kuisu, the rest of the Kamidake crew were still only girls.
Kiriko gets a chance to negotiate with the Renza gang, not only determining their names and not so shockingly their affiliation to the extant Renza kingdom. They are accused of several offenses, such as stowing aboard the wedding barges which by itself is a major breach of trust within the much larger Jurain political apparatus.
Seina is taken for a stroll by Kuisu throughout the Racepshi, the motive seemingly to get down to business. However, many misunderstandings ensue, and it is with Seina's crude understanding of cultural equivalency that he somehow manages to break free. As if to compromise, one of the crew gives Seina a private exotic dance, but after is amazed when he again he refuses to sleep around so sporadically.
Aboard the starship holding him somewhat captive, there are many remarkable species native to the Renza controlled pocket of space. However, more pressing to him and his rescuers are the matter of the Racepshi declaring their ransom void and forking over their share of the wedding fees. Nonetheless, the ship is attacked and with Kaguya's help Seina learns the use of countermeasures against Light Hawk Wings should the attackers be Jurain royalty. Instead, they are a pursuit detail under orders from Baron Kamui Kahurun Kasen. They express great interest in getting to see ZINV in battle again. But then HIMIK appears. Everyone panics.
Amane asks D about the nature of parallel worlds, and how ZINV seems to be involved in much of it. It looks light a big fight is about to ensue, so the two of them try to access the battle records within ZINV to get some kind of strategic advantage. But the Kamidake is barred from leaving the Racepshi.
Right as Seina manages to board the ZINV and try to activate it from the cockpit, the attending factions are stunned as HIMIK takes out their sensor gear from long range. Before long, both ancient mechs are using LHW-tier abilities against one another. The Kamidake crew debate making an escape in light of the fierce fighting and the position the Racepshi have taken on holding them there for a tentative amount of time.