(from ebookjapan):
The last words of President Kennedy, who was killed by a bullet, were "Directive 0." Eight years later in Japan, three boys, Minamoto, Taira, and Ichinoki, are training to become Class A Knights of the Kennedy Knight Order.

The plan of the Kennedy Knights is to select boys with a pure and strong sense of justice from all over the world and protect world peace beyond national borders. The boys are very active under the motto of "Ask not what the world can do for you – ask what you can do for the world."