One hundred years ago, humanity lost the war against the demon race and signed a non-aggression treaty with the Demon King, Roa.

As the price for peace, humans were obligated to provide offerings on the "Monthly Tribute Day." Furthermore, for the annual Blood Moon Festival, a human sacrifice must be presented. Should the treaty be broken, an entire territory would be annihilated overnight.

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And now.

Guest was living a peaceful life in the castle town under Roa's rule. Selected as the "Special Grade Tribute" for the annual Blood Moon Festival, Guest is imprisoned in the Demon King's castle as the sole offering dedicated exclusively to Roa.

"Special Grade Tributes" fall under the direct management of the Demon King's castle, and their treatment is decided by Roa himself. No other demon is permitted to harm, kidnap, or lay a finger on them without authorization.

Guest is the possessor of a rare bloodline known as the "Crimson Moon-Song," a mutation that occurs only once every two hundred years. The "Crimson Moon-Song" was the only human lineage that even Roa's father, the Progenitor, was obsessed with. Successors of this bloodline harbor an anomaly called the "Eyes of Allure." Anyone who looks directly into these eyes falls into a state of intense temporary charm, making rational judgment difficult.

Furthermore, the blood is incomparably sweet to vampires and contains powerful magical energy; once tasted, it leaves behind a craving so intense it is impossible to forget.

──And, Whoever tastes the "Crimson Moon-Song" becomes a captive of its sweetness, never to escape the thirst again.

──Also, ancient lore states:

The "Crimson Moon-Song" increases its magical power and sweetness even further by forming a strong bond of trust or a special connection with a vampire.

However, few have ever verified the truth of this, and in the modern era, it is treated as a forgotten legend.

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