Ryo-Ohki is Ryoko's sister, both being Masu hybrids created by Washu, and she also serves as Ryoko's spacecraft. Similar to Ryoko, Ryo-Ohki can phase through solid objects and is friendly with everyone, particularly Sasami. However, it's important to note that in her ship form, she only takes orders from Ryoko.
When Washu was imprisoned by Kagato, she and Ryoko attempted to capture the Tsunami tree on planet Jurai but failed. During their escape, they were shot down above Earth while fleeing Yosho's ship, Funaho. Ryo-Ohki then remained in a deep underwater sleep for seven hundred years until Tenchi broke Ryoko's seal.
The current Ryo-Ohki is a second-generation entity; the original died of old age but regenerated by creating a child with its memories, taking the form of a cabbit (part cat, part rabbit).
The smaller form was created by Ryoko after her revival. Before leaving the cave, Ryoko watched over Tenchi constantly in an astral form and fed some of her power to a dying cat he was caring for to keep it alive. Upon her revival, she had to reclaim this power, so she had it assimilated by Ryo-Ohki.
Ryo-Ohki's power is comparable to that of the second-generation Jurai tree-ships. Although she cannot create Light Hawk Wings, she temporarily gained this ability by assimilating Ryu-Oh but lost it when Ryu-Oh was destroyed. Nonetheless, she seems to have a friendship with him, as she can be seen communicating with the newly born sapling Ryu-Oh.
In the OVA series, Ryo-Ohki acquires two humanoid forms: one of a child and another of a teenager. She prefers the smaller form as it's easier to maintain her balance.
