Kokuha Kuzumi

She is Kuzumi Taiga's older sister and is 19 years old. She is very short for her age and is often mistaken as the younger sister instead leading to a complex about her height. She was a rising star in karate during her grade school and middle school years, so much that Kumi admires and wants a match with her, though was told to fortify her body first. Due to Kokuha practicing on Taiga constantly, he became much tougher than most people would. She also had a one-time infatuation with Kenjiro Hiiragi, though upon mistaking her an elementary school girl she felt rejected and proceeded to beat Kenjiro severely. (Wikipedia)