C.C. is an immortal girl who outwardly appears to be little more than 16 years old. She becomes Lelouch Lamperouge's accomplice when he makes a Geass contract with her. She is willful almost to a fault, usually doing whatever she wants regardless of whether or not it inconveniences others, particularly with Lelouch. She also likes to withhold information, usually telling people just enough to leave them wondering. C.C. has a strong penchant for pizza, especially Pizza Hut's (which sponsors the show in Japan, though the logo is blurred out in the English dub); she constantly orders pizzas to Lelouch's house using his credit card. She also carries around a stuffed toy of "Cheese-kun", the company's mascot in Japan. Her love of pizza is often used for comedic effect, as she was twice willing to risk capture simply to get a piece of a giant pizza being made by the Student Council (which is ruined both times). Both Lelouch and Kallen sometimes refer to her as "Pizza Girl".
Her individual experiences have led C.C. to become a detached and lonely individual (though she usually tries to hide it, especially around those she does not know well), with little care for even those she has entered into contracts with, while in the past she was somewhat a spoiled and cheerful girl. She tells Lelouch that she has been alive so long that she can no longer remember who loves her and who hates her. Due to her nature and history, she has been lonely as long as she can remember. Lelouch replies, "You're not alone. We are each other's accomplice. If you are supposed to be a Witch, then perhaps I should be a Demon." Lelouch is possibly the first person that has ever truly cared for her and it appears that she reciprocates at least some feelings, as she unexpectedly kisses him after their memories are shared. However she claims that she has only been using Lelouch so that she can die. But in episode 23 of the second season, Suzaku describes her as Lelouch's shield, protecting him from his enemies. Also, in episode 24 when she was fighting Kallen, Kallen stated that she has no will or ambition to fight, and she replies she has a promise prompting Kallen to ask if she loves Lelouch, C.C. replies with a glance down saying she doesn't know, referring to her relationship with Lelouch thus far. When left alone, she has sometimes spoken to a previously unknown person through means unknown, which, in episode 23, was revealed to be Marianne, Lelouch's deceased mother, although in episode 19 it appears that she is talking to V.V. as well. According to the DVD Magazine 02, she is talking to more than one person when she seems to be talking to herself. She gave Marianne the power of Geass and therefore had the same relationship with her as she now has with Lelouch.