A single bullet cuts through Kyoto in the last days of the Tokugawa shogunate right before the restoration of imperial rule. Who plotted to assassinate Tokugawa Yoshinobu, who is about to become the last shogun of Japan? Was it the faction wanting to overthrow him or the rebels within the shogunate? Mutual enemies Sakamoto Ryoma, the wandering samurai, and Hijikata Toshizo, a deputy leader of the Shinsengumi and vassal of the Tokugawa clan, receive a secret order to track down the culprit. They are given a mere two days.

将軍暗殺を企て、幕末に戦乱を起こそうとしたのは、いったい誰なのか？ そして、龍馬暗殺の真犯人は！？ さらに新選組史に残る「油小路の決闘」の真実 が明らかになる！ 土方「隊士一同に伝えておけ。坂本に手を出すなと。 あいつを斬るのは俺の役目だ！」 龍馬「いま戦を始めたら、日本はバラバラになるぜよ。 けんど、お互い信じ合えたら、一つになれる！」