Guardian Systems, sometimes called Guardians or, in certain forms, a Guardian Suit, are somewhat common weapons in the interstellar civilization of Tenchi Muyo.
Two styles have been described in the Tenchi Muyo metaverse, the more common type are largely electronic versions that can be discreetly attached to the user and called upon by its user, but Jurai has also been shown to use wooden guardians that are separate from the user and can contain a level of independence from their user.
Description

Shou's new Guardian in OVA5
The Guardian System is a technology that typically creates a force field that acts as both a suit of armor, and a weapon. The specifics differ from System to System, with some having melee weapons built in, to long range, or even more unique weaponry. When deployed, the usual Guardian System has a vaguely humanoid appearance that surrounds the user.
It's revealed in Paradise War that Guardians were originally specialized defensive clothing, which may explain how the Kaunaq clan got into the fashion industry after starting out making Guardians. Now, Guardians are suits of armor made of force fields. They are produced by nanomachines that can be implanted in the body.

Azaka and Kamidake.
Guardians can also function apart from the user and can have a level of Artificial Intelligence. The earliest we see Guardians in the anime, they are in a very different form than the now typical "body armor" described in novels and shown in later installments, but still basically serve the same purpose. Azaka and Kamidake are the Guardians of Ayeka, however, they are not part of her. Instead they have their own "log" form and, on command, can project a powerful protective barrier. She can also materialize smaller wooden Guardian terminals she can use for defense or offense.
It is also explained in some instances that a Guardian can be placed on a person without them knowing it and will only show itself when the person needs them. In True Tenchi Muyo! Volume 2: Yosho, Yosho becomes concerned that Airi will be attacked, so he gives her a ring made from the wood of Funaho. When she is attacked, a powerful forcefield surrounds her and repels her attackers. In Paradise War, Shou Kukoma had a Guardian implanted in his skin during his first physical examination by Miron, this acts like a more traditional "suit of electronic armor" but it initially only activated when he was attacked. And most recently, Washu explains that, while he is training, Kenshi also has an implanted Guardian, but he has no knowledge of it and it will only activate if his life is truly in danger. Presumably, it was removed before he was sent to Geminar, as they wanted him to have no extra physical enhancements.
Trivia
- The first appearance of a Guardian System that surrounds the user was by Tarant Shank, during his attack on the GXP ship where he first encountered Kiriko and Seina Yamada.
- It is suggested that the Galaxy Police's original combat Guardian Systems were originally developed by the Kaunaq family, prior to their becoming fashion moguls. Likely, this was before they became the present suits of armor, and were still clothing.
- The current Guardian designer is Raireza, a philosopher that works under Airi.
- The Guardian Systems play a large role in the series, Paradise War.