Haku

Haku is a ninja from the land of water. He has the ability to control two types of nature chakra (most can only control one), they are water and wind chakra. This gives him the ability to use ice chakra which is a mixture of the two. Haku's ability to use ice is his kekki genkai, which is unnamed in the series.

The Land of Water was suffering from war, ninja like Haku were hated. This caused Haku's father to kill his mother, but before he could kill Haku, Haku killed him. After that Haku met Zabuza, seeing the potential Zabuza began training Haku as a weapon. Kakashi later kills Haku when he was trying to kill Zabuza.

It is revealed that Haku and Zabuza met Kimimaro sometime while Zabuza was a part of the Hidden Mist Village.