|“||Hehe, how is it? You can't do anything, can you? A man that cannot do anything, is a man that nobody needs. I'm going to kill you.||”|
–Cao Cao Sisters to Kinji Tohyama, Volume 6, Chapter 2
The Cao Cao (or Koko in Japanese) Sisters: Juju, Paonyan, Meimei, and Jinyang, are members of the Ranpan Hong Kong branch, where they tend to cause trouble for the organization in an attempt to usurp their leader, Seigen Shokatsu, authority. Juju, Paonyan, and Meimei were introduced when they attacked Kinji Tohyama, Reki, and Aria H. Kanzaki during the fallout after the collapse of IU. The fourth Cao Cao sister, Jinyang, appeared later on during the conclusion of Volume 12. All four them would be enemies during the Far Eastern Warefare (FEW) where Ranpan had sided with the Greneda faction. After Ranpan defeat, they would become part of the Deen faction.
Kinji described the Cao Cao sisters as being very cute in appearance to the point where men would drool and being similar to Aria. The sisters all have long black hair tied in twin tails with a double bead holding it in place, the corners of the eyes streaked with red eye shadow, and wear a white colored, modified version of the Qing Dynasty dress. The sisters are in distinguished from each other, except for Jinyang, who wears glasses.
The Cao Cao sisters personality are similar to Aria by being childish and short tempered. Also, they are devious as shown when they tried to seduce Kinji into joining the Ranpan by being his wife/concubine as well as acting without Shokatsu authority.
- (Cao Cao comments about Tokyo Butei High): "Japan's Butei High isn't very noteworthy. You're too vulnerable." (Volume 6, Chapter 2)
- (Cao Cao introducing herself to Kinji): "My, name, is Cao Cao. Tell me your name." (Volume 6, Chapter 2)
- (Cao Cao to Kinji after defeating him): "You have to study. Afterwards, I'll test you again. Goodbye." (Volume 6, Chapter 2)
- The double beads holding the Cao Cao sisters twin tails in place is similar to Kotomi Ichinose's hair beads from the Clannad series.
- Each of the Cao Cao sisters represent a different part of a strike force:
- Juju = Sniping
- Paonyan = Assault
- Memei = Assault and Explosive Technician
- Jinyang = Logistics and Weapons Development