Ten years have passed since the end of Bakumatsu, an era of war that saw the uprising of citizens against the Tokugawa shogunate. The revolutionaries wanted to create a time of peace, and a thriving country free from oppression. The new age of Meiji has come, but peace has not yet been achieved. Swords are banned but people are still murdered in the streets. Orphans of war veterans are left with nowhere to go, while the government seems content to just line their pockets with money.

In this world, creatures like vampires and werewolves still walk about, but Aya Rindo can’t say the same for herself. This beautiful disembodied head, carried by her maid Shizuku Hasei, is a detective in search of her stolen body. One evening, they meet half-human Oni Slayer Tsugaru Shunichi, who offers a lending hand. Now, the trio is traveling through Europe, solving mysteries along the way.