Okada Izou… "Izou the Slayer" is coming to America!? At the recommendation of Ryoma, Izou is assigned to escort Kaishuu Katsu, the military magistrate of the Tokugawa Shogunate, to travel to San Francisco on board the Kanrin Maru with a Japanese delegation to ratify the Treaty of Amity and Commerce between Japan and the United States. At the welcoming party, Izou is upset by the arrogant attitude of his patron, Richardson, and causes a big fuss. This leads to Izou's decision to stay in the United States! He travels all the way from the west coast to Washington, D.C. Along the way, he encounters various events and historical figures…

With delicate depiction and detailed world setting, the author has created a fantastic hero that transcends dimensions. And together with the hero boy Hiroki, they fight against an epic destiny and a powerful enemy to protect two worlds. Hiroki's destiny calls for a nemesis, and the battle gives birth to tragedy. Primus always comes to Hiroki's rescue when he is in danger. However, Hiroki's life is shortened when he uses Primus' power. What will the contract between the two bring about in the two worlds? (Source: Kodansha, translated)