Dokuro Mitsukai is a cute angelic assassin from the future brought back through time to kill Sakura Kusakabe, but instead tries to save him. Mostly, she is just like any other young girl but where other girls might shout or slap to express their displeasure, Dokuro draws her magical spiked tetsubo "Excalibolg" and brutally clubs her victim to death with it. She's also capable of bringing someone back to life with Excalibolg by chanting Pipiru piru piru pipiru pi (the refrain of the theme song in the opening credits). When she isn't brutally killing Sakura she teases him mercilessly, mostly using sexual innuendo.
source : wikipedia