In Koihime†Musō she made her initial appearance as an ancillary general, fighting with Kōsonsan against the Yellow Turbans. In her debut she ventures out, against Kōsonsan's objections, and takes on an entire army of Yellow Turbans alone. Although Kōsonsan chides her foolishness, Kazuto, from his knowledge of the Three Kingdoms, realizes that Chōun is a powerful warrior who would become a valuable comrade. So despite the danger of being annihilated, Kazuto is set on rescuing her should she get in danger.
On the battlefield, Chōun manages to deal massive casualties among the Yellow Turbans but eventually encounters trouble. At this moment, as planned by Kōmei, Kan'u intervenes and the two back-to-back slaughters their way out of the enemy mob. After defeating the Yellow Turbans, Chōun meets Kazuto and immediately takes a liking to him. She states that she will be traveling the continents for a while to see the world with her own eyes; however she promises to join him if she fails to find a better master. She officially joins hims alongside Kōchū after the battle with Enshō.
In the Gi route she saves Kazuto from the three bandits and leaves shortly before Sōsō's army arrives. She appears again during the anti-Tōtaku campaign serving under Kōsonsan. After Kōsonsan fell to En forces, she joins Shoku faction.
Chōun is a mysterious girl who first appears serving under Kōsonsan. The second person to join the group, she loves to tease Kan'u and others frequently, and seems to relish whenever she gets up close with them. Like in the VN, she also assumes the identity of a hero of justice named Kachō Kamen by wearing a butterfly mask. She tries to recruit Chō sisters into joining her at the end of Shin Koihime†Musō but gets ignored, despite making a dramatic entrance and delivering a grand speech.
In the first OVA, Chōun (as Kachō Kamen) appears for the swimming event, but Kōchū, who is acting as the judge, begins to comment on the similarities between Chōun and Kachō Kamen. Before she could say too much Chōun ties her up and lockes her in the gym storage shed; no one seems to notice her missing, not even Riri.
In the VN she is shown to be calm and collected with a playful, sometimes flirtatious, air around her. While she rarely loses her temper, she turns dangerous if someone were to touch her menma and alcohol without permission. Like Kōchū, her rage is cold and calm but at the same time terrifying and even creepy. However, unlike Kōchū, she is usually straightforward and blunt, lacking much sense of shame. Of Kazuto's harem, she can be considered "the weird one" who loves to throw in a bit of chaos just for her own amusement or to make a point. She has an off-beat personality and tastes that run quite differently from everybody else's.
In the anime she is portrayed in a less serious manner. Although introduced as being calm and collected, her weird and mysterious side quickly shows. She is well-known for making perverted remarks at the most inappropriate times. While she most certainly has knowledge of love and sex, most of the times when she makes a perverted joke she does it with a straight face, as if she doesn't know it is inappropriate to make such a comment. Her randomness and ridiculousness increase as the serie progresses. There are plenty of moments during which she acts like a jerk, teasing the other girls in the most embarrassing manner. She is also a bit egoistical, although she is smart enough to not to act outright arrogantly. For example, she (as Kachō Kamen) saves Ryūbi from bandits, causing Ryūbi to develop a crush on Kachō Kamen. After coming back, Chōun asked Ryūbi who saved her, and in response Ryūbi begins to say good things about her, raising Chōun's mood high. When it comes to Kachō Kamen, Chōun has a wild imagination that comes up with crazy and fanciful stories and entrancing speeches.
In both versions, she has a strong obsession with menma. She also show some chūnibyō tendencies, having a habit of running around the city as the masked hero of justice Kachō Kamen ("butterfly mask") in her patrol shift. To complete her alter ego she also make poses and stylized speeches. Strangely, no one other than Kazuto and Kōmei can recognize her true identity, despite adding only a mask to her normal clothing and using the same weapon and fighting style. Furthermore, Chōun herself doesn't recognize how obvious her disguise is to Kazuto. when not being delusional she is actually quite graceful and elegant in her behavior.
In the first VN, she proclaims herself the second master of love in the Three Kingdoms. She, along with Kōchū (who is the first), frequently give Kazuto advice in his love affairs. Interestingly, despite her seductive front, she can be surprisingly pure at times which shocks Kazuto. In the beginning she has a rather skewed idea of how sex works, since all of her knowledge at that point comes from spying the soldiers masturbating in their tents. With this awareness she manages to give Kazuto a handjob with no problems. Unsurprisingly, her information is limited to the male anatomy; on her first night with Kazuto she actually thought that "pillow games" is simply pillow fighting. Kazuto soon proves her wrong and she learns what actual intercourse is. Afterwards she learns quickly and soon enough she becomes one of the most knowledgeble on the topic. Due to her bold and open nature, she easily agrees to pair up with Kan'u for a threesome and she has no problems with Kazuto establishing a harem.
Spearsmanship: Chōun is famous for her spearsmanship, and her counterpart in the Romance of the Three Kingdoms is a spearman second only to Zhang Fei. Compared to her fellow spear-users Chōhi and Bachō, her spear is a stab-only weapon; she specializes in speed and agility and is most notable for her graceful manner of fighting, where she seems to "dance" on the battlefield while dishing out quick yet deadly jabs with her spear. In the first VN she fought against an army of 25,000 Yellow Turbans on her own for a time, encountering difficulties only because she killed too many enemies, causing piles of corpses to impede her movements.
Expert Hand-to-Hand Combatant: As Kachō Kamen she has demonstrated proficiency in hand-to-hand combat.
Enhanced Physical Prowess: Her strength, speed, reflexes, and stamina are above those of normal soldiers. As Kachō Kamen she is very acrobatic to the point of being able to balance perfectly still on the tip of Kan'u's guan dao. Even in everyday life she has shown a preference for high places.
Leadership Skills: She is an excellent general and is able to command large troops proficiently. Furthermore, Kazuto has likened the troops under her command to a modern commando unit.
Horsemanship: She knows how to ride a horse and can maintain control over her mount even amidst the chaos of battle.
Marksmanship: In the anime she is able to throw her butterfly masks in a shuriken-like manner with great accuracy and control.
High Intellect: She is very intelligent, displaying considerable wisdom and understanding of strategies in both battle and government affairs (although she shows a tendency to operate behind covers). Furthermore, she is flexible and quite creative in thinking. During battle, she is very perceptive and takes a more strategic approach when compared to many other generals but has been shown, in her first introduction in the VN, to work herself to a frenzy.
Zhao Yun is associated with the color white in many Three Kingdoms media.
Her voice gets deeper in the anime.
Her character design might be based on Rei Ayanami from Neon Genesis Evangelion. Both have short blue hair and Chōun's weapon resembles theSpear of Longinus.
Likewise her character design, plus personality, might be the basis for Tatenashi Sarashiki of Infinite Stratos.
While hardly serious and even delusional at times (especially so in the anime), her intelligence should not be denied. In Hongō/Shoku faction, she is a person of both brain and brawn, alongside Kan'u, Gengan, and Kōchū.
She unofficially handles military intelligence.
Her obsession with menma is so great that she can eat it straight out of the jar despite it being a condiment.
In the second OVA she even dips it in chocolate fondue.
Her Kachō Kamen stunt is a reference to the Super Sentai genre.
In the anime, she explains that she became Kachō Kamen after dying and then resurrected by a mysterious being hinted to be Ultraman.
In the second OVA she actually transforms Ultraman-style, becoming huge via wearing her butterfly mask. In addition, her nipples light up and blink after a certain time period. This is her version of Ultraman's Color Timer.
Unlike the other girls, she calls Kazuto "aruji" rather than "goshujin-sama".
She gets her own ending in the PS2 version of Koihime†Musō
In the anime it is implied that she can pull an extremely disturbing face. She first does this as her "good face" for people to remember her by. Although the viewers can't see her face due to the scene portraying her from the back, Bachō will have nightmares about it and Kōchū simply covers the eyes of her daughter while staring in horror.
On another occasion she is shown from the front and her face is actually censored.
In Shin Koihime†Musō LIVE Revolution she (as Kachō Kamen) plays the guitar.
Interestingly, despite all her openness in sexual matters, in Shin Koihime†Musō manga she states that Sōsō's tastes don't really suit her.