Seat Number: 10
Completed: March 1, 2001
Activated: January 4, 2002
Hair: Light green
Eyes: green
Spring Powered model (initially external power source)
Likes: Having people wind her up, serving Tea
Dislikes: Nothing, really...
Belongs to the: Tea Ceremony Club, Go Club

Chachamaru Karakuri is student number ten in the class. She is a two-year-old robot created by Satomi Hakase to serve Evangeline and protect her during time where the spell binding her weakens her. She is initially without any real emotions, but after spending time around Negi, she begins to have feelings for him, and show emotions, such as embarrassment when the crush is brought up, her internal gears increasing in speed during moments where a human's heart would beat faster, and even leaking laser fluid from her eyes when she's upset. These feelings go against her original programming, which excites Hakase. She spends most of her free time helping people and rescuing stray animals. She strongly fears the idea that she is nothing more than a soulless doll and that she does not have a soul; however, during the Governor's ball in the Magic world she forms a pactio with Negi (in Nagi form) which appears to have a cat theme, proving that she does indeed have a soul; as Pactio contracts can only be formed between those with true souls.

Chachamaru's body is powered by an internal spring combined with magic, and it has to be wound with a key by someone with magical energy to power her. The actual winding process is apparently pleasurable and/or arousing, although too much magic can intensify the feeling to uncomfortable levels. She is skilled in hand to hand combat, and she is equipped with rocket fists, laser emitters, magic-powered thrusters that can allow her to fly for fifteen minutes, and a tool to undo binding circles. Her body has been upgraded several times, and she is later given a completely new body that looks completely human, unlike her original body's easily detectable parts; she even has a chibi body designed to disguise herself. The upgrade also allows her to transform her arms into swords and guns.