The main character, Yumeno Kawashima, is assaulted by a yankee, Benine. A group of three ninja girls who call themselves "Sailor Ninja Kagechiyo" happen to be there by near miss. When Kagechiyo hears what happened, she promises to avenge Yume's death. However, for some reason, Yumeno also decides to train as a ninja because "it's better to have as many people as possible.