Kirihara Touko

Touko is a descendant from a samurai clan. She used to go out with Taichi. Currently, she is very harsh to him. "Kirihara" is an anagram of Harakiri, which Taichi sometimes uses as her nickname. She scored 44% on the adaptation exam, and as Taichi says at one point, is "desperately trying to hold on to the last 56% of her humanity as best she can."

Edited from Wikipedia