Billionaire Tono Ryuichi, President of the food giant Tono Foods Group, has recently acquired two young female assassins from a Mexican cartel. Sui and Ai endured unimaginably impoverished childhoods and were presented with a choice between killing people or selling their bodies. They chose the former, underwent inconceivably extreme training, and by the age of 17, had become among the deadliest assassins in the world. They remain absolutely obedient to their master and have been tasked with finding the killer who poisoned Ryuichi's wife and child. To blend into society, they begin attending high school, while simultaneously reading and studying, which helps them become even deadlier in the field. Sui and Ai encounter Matoba Imari, a high school assassin in her own right who may be more skilled than both of them. Unlike the pair, however, Imari simply wishes to lead a normal life. Whatever Imari desires for her life is not their concern, as the only things Sui and Ai feed on are bloodthirst and a challenge.