Nana, a handsome, young boy with long fair hair who suffers from extreme amnesia, has forgotten his real name. After helplessly witnessing the unjust death of three children during one of his trips, he vows to eradicate all wars on the surface of the earth.

He then joined Tripeace, a small group of activists whose members use all kinds of weapons and will stop at nothing, not even the violence, bring peace to the world. But soon, the new registration number 102078 of Tripeace is faced with a dilemma: can we protect the peace at any price?

Although he is well trained in combat, Nana is very good at disguising and passing himself for a woman. He uses it to cheat his enemies and get advantage when in mission. When in woman mode, he uses the name Nanako.