Carve-tan

"Carve-tan" or occasionally "Kabeko" is a student at Ashford Academy.

Appearance
She has shoulder-length dark blue (or black) hair. She appears to have dark green eyes, however, they are always surrounded by the red-effect caused by Geass. It seems this redness continues even after she's made her mark of the day as she is shown to still have it as she walks away.

First Series
A schoolgirl at the Ashford Academy that Lelouch uses his Geass on to test how long the effects lasted. He used it to make her make a mark on a wall everyday at a certain time, he checked the wall every now and again to confirm she was still under the effects of the Geass. He uses this to assure himself the effects of Geass could work long-term.

Second Series
In the second series, Lelouch walks past the wall and sees that one of the marks stopped half-way.

It has been stated that she was safely evacuated from Area 11, but was still under the effects of Lelouch's Geass, meaning that every night (due to the time difference) she would escape from her home and try to return to the wall at Ashford, which resulted in a nervous breakdown. She had to be confined to prevent her from escaping, but apparently she's doing better now.

Trivia

 * Lelouch realizes he screwed up her life by abusing the power of his Geass to turn her into an experiment.
 * Her name is a nickname created by the fans since her real name is never said. She has been called "Carve-tan", "Kabeko" and sometimes "The girl making wall marks"
 * Her appearances simply show her making marks on the wall.