She makes her first appearance fighting against the Yellow Turbans. With her army badly losing, Gakushin's relieve force arrive to help and she retreats. She is not seen again until the anti-Tōtaku campaign, where she is assigned to guard Sishui Pass. However, she loses and retreats to Hulao Pass. To avenge her previous loss, she charges out only to be badly beaten again. She retreats with Chōryō and Ryofu after order came to abandon post. After the fall of Tō she is mentioned to have been defeated by Kan'u, though she appears alive and well in the epiloge, traveling with Enjutsu.
A brave general of the Tō army, she has absolute confidence in her fighting skills. She is also easy going as she doesn't mind if her leader Tōtaku goes visiting commoners in disguise, as she believes it will help their country's welfare if she sees their problems through her own eyes.
At almost 6 feet in height, she is the tallest girl in the series.
She's notable for being the only girl that doesn't have a romantic event in any of the VNs.
She does not die in the anime (at first she appears to have died in action, as she walks out to battle and never comes back. But she later returns, the reason for her absence being having gone into hiding).
For the sake of irony, in the anime she keeps saying that she's the type who lives a long life.
In a next episode preview of season one, Kayuu claims the right to announce the episode title because she's going to "die early".
Guanyu slaying Huaxiong is actually a famous scene in Romance of the Three Kingdoms.
Despite officially listed as having a combat rating of 4, in the bonus Han route of the second VN she fights toe-to-toe against Chōsen and Himiko, both of whom have combat ratings of well over 5.
It's revealed in the Go route that she has been defeated at the hands of Sonken Bundai.
Chōryō Bun'en once calls her "Miyabi" (雅 Ya) at Sishui Pass, this was never brought up again for unknown reasons, and many suspect it to be Kayū's true name.
In the harem ending of the first VN, during the last scene, there's a unidentifiable figure standing next to Kōsonsan. It maybe Kayū based on the hairstyle and the process of elimination.
Likewise, although seemingly killed and forgotten in Shin Koihime†Musō, she makes a cameo appearance in the end scene of Moe Shōden.
Her tendency to being forgotten about is actually a running gag. In Moe Shōden during the creators' commentary special, she delibrately breaks the fourth wall to remind readers that she is present at the end of Moe Shōden by zooming in on herself.