The year is 1863. It is a turbulent time in Japan, as rising anxieties about the modernizing world coincide with the decline of the shogunate, and the possibility of civil war looms. As disgruntled samurai flood into the city of Kyoto, a group of warriors are recruited to maintain peace and protect the shogunate's interests: the Mibu Roshigumi, later known as the Shinsengumi!

Danger seems to lurk around every corner in Kyoto, and a cabal of well-hidden imperial loyalists is slaying the Shogun's supporters from the Aizu Clan. When the daimyo of Aizu contracts the Mibu Roshigumi to investigate and bring the killers to justice, it seems like the perfect opportunity for the cash-strapped group to find a powerful patron who will bring them under his wing. But how will they find an enemy hidden in plain sight, and what will the trio of boys from Kyoto--Nio, Hajime and Taro--be able to do against grown hit men?