It is the 12th year of the Taisho era, and those will appear on the night of Tokyo. They are vampires that lurk in the darkness and sip human blood, and have lived in this world invisibly since ancient times. The 16th Special Forces was created within the army to manage them, commonly known as the "Zero Agency". This unit was created by Lieutenant General Nakajima to fight against the intelligence war of the modernized powers, but the current mission of the Zero Agency is to respond to the vampire incidents hidden in Tokyo. Those assigned to this task are Colonel Yoshinobu Maeda, the strongest human, Hidetaro Kurisu, the highest-ranking vampire in the country and a newcomer to the agency, Tokuichi Yamagami, whose intelligence is out of the norm, Suwa, who has existed since the Edo period, and Takeuchi, a mad scientist who loves unaged brains. The above are the members of the Zero Agency's implementation team. The increasing number of vampires, the shadows acting in secret, the existence of mysterious artificial blood, and the one who is watching these events with a cold eye is the S-rank vampire Devrot, who is over 300 years old but looks like a child. Zero Agency Today, travels through the romantic night of Taisho.