Mana Itosu

Itosu is very polite and acts more level-headed compared to Ruka who has an opposite personality compared to hers.

She is also very polite in the real world as seen during her meeting with Kuroyukihime and she holds high regards for her master and the rules that he set for her and Ruka.

Itosu became the child of Ruka after she became a burst linker. After becoming a burst linker, she and Ruka are inspired to to increase the number of burst linkers in their community.

(Source: Accel World Wiki)