The fate of Japan is at stake… The year is 1868. A war is about to break out in Boshin. The Templars have infiltrated the inner circle of the emperor's advisors, urging him to launch a campaign against the shogun Tokugawa, who is supported by the Brotherhood of Assassins. A sixteen-year-old Japanese girl, Atsuko, has grown up in the prosperous district of Aizu city in the shadow of her brother Ibuka. She is being arranged to marry for convenience, but she has a secret: she wields a weapon as skillfully as her brother. And behind her brother’s talent lies an overwhelming fear of battle. When the war begins, Ibuka must go into battle to protect the family’s honor. Atsuko wants to protect her brother and, defying the tradition that forbids women from participating in battles, secretly enlists as a common soldier. She dreams of proving her abilities to everyone, but soon encounters manipulations and conspiracies that are too serious and dangerous for two teenagers. What will prove stronger: brotherly love or convictions and honor? Will the great era of samurai come to an end?