Tsundere (ツンデレ, Tsundere?) is a Japanese character archetype that describes a conceit, spikey, combative personality that later on turns to being modest and loving. It can also describe a personality that is good-willed, but its attitude and actions often contradict its nature. Originally found in Japanese galge, the word is now part of the otaku moe phenomenon, reaching into other media such as anime, manga, novels, and even mass media.
They also tend to have pigtails and be voiced by Rie Kugimiya.