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Cao Cao was the leader of the Hero Faction of the Khaos Brigade. He is the wielder of the Ultimate Longinus, the True Longinus. He is also the descendant of Cao Cao from the Chinese novel Romance of the Three Kingdoms. In Volume 17, Cao Cao becomes Indra's vanguard after Sun Wukong gives up his position.
Cao Cao is a handsome young man with short black hair. He wears a combination of a Japanese school uniform (more specifically, the gakuran worn by Japanese schoolboys in the fall) and ancient Chinese attire. He also lost his right eye while escaping from the Kyoto incident but later gained one of Medusa's eye, restoring his sight. After his battle with Issei Hyoudou in Volume 12, he lost his Medusa's eye and since Volume 18, wears an eyepatch.
Cao Cao is a charismatic and manipulative person, as he was able to convince many Sacred Gear users to join the Hero Faction either from their own will or by brainwashing them. He also believes that it is his responsibility as a descendant of a hero to destroy beings like Devils, Fallen Angels, and Dragons which he believes are threats to human beings. Like his ancestor, he has the eyes to find people with good potential and considers them valuable talents. However unlike his ancestor, Cao Cao only accepts Humans with Sacred Gears in the Hero Faction and wants to see how far his faction can go against supernatural existences as he wants to test the limits of what humans are capable of.
Birth of the Breast Dragon Emperor
Cao Cao first appears in the end of Volume 6, talking with Siegfried on the defeat of the Old Satan Faction, sarcastically saying that it is too bad their Dimension Lost user did not go all out to which Siegfried replies that it was Cao Cao who gave that order.
The Heroic Oppai Dragon
In Volume 7, Cao Cao is seen talking with Siegfried who warns him that they are close to being discovered, to which Cao Cao replies by saying that they have gathered enough talent and can start the next phase.
In Volume 9, Cao Cao made his official appearance to Issei and his friends during their class trip in Kyoto. He and the rest of the Hero Faction were responsible for the kidnapping of Kyoto's Youkai Leader, Yasaka, with the intention of opening the Dragon Gate to summon the Great Red. This attempt, however, was stopped by Issei and his friends along with the last minute intervention of Sun Wukong. In the process, Cao Cao lost one of his eyes to a final blow from Issei.
Cao Cao reappears in Volume 11, attacking the Gremory Team in order to capture Ophis. During the fight with assistance from Georg while targeting the weakness of his opponents, Cao Cao was able to dominate the battle, defeating the Gremory and Vali Teams, even shattering Xenovia's Ex-Durandal in the process, and successfully stole Ophis' powers.
In Volume 12, he appeared in the Underworld after Issei and the Gremory Team defeats the Hero Faction, challenging Issei to a fight, which Cao Cao was able to dominate, but eventually lost after Issei used a bullet with Samael's blood on his Medusa's eye weakening him. In his last attempt to defeat Issei, Cao Cao attempted to use the Truth Idea but did not happen due to the will of the God in the True Longinus choosing Issei's dream instead of Cao Cao's ambition. He was then rescued by Georg who carried Cao Cao and Leonardo until they meet Indra who proceeded to take their Longinus and sent Cao Cao and the other two to the Realm of the Dead.
The Legend of Oppai Dragon and his Lively Companions
Cao Cao returns from the Realm of the Dead in Volume 16, reclaiming the True Longinus from Indra, who complimented Cao Cao on his return, to which Cao Cao replied saying that it was Indra who sent him there in the first place.
Although Cao Cao did not appear in person in Volume 17, he used his True Longinus to break through the barrier created by Ladon surrounding Auros, thus helping D×D.
Cao Cao helped defend Heaven from the attack of Qlippoth in Volume 18. He fought against Ladon and was able to trap him inside a crevice for Rias to use her Extinguish Star to destroy Ladon's body and for Koneko to seal his soul inside a jewel that came from Issei's armor. When asked why he returned, Cao Cao replied that he wants to know why the True Longinus was given to him.