Chifuyu is Ichika's older sister, and homeroom teacher of his class at the Academy. She was the Japanese pilot for the first-generation IS machines and was said to be the strongest IS pilot at one point before retiring. During her retirement, she looked after her brother and raised him by herself after their parents abandoned them at a young age. Despite her indifference towards Ichika, Chifuyu deeply cares for her brother, as she sees him as her only family. Chifuyu was also the one who enrolled Ichika to the IS Academy to keep him safe from other countries. [From Wikipedia]