In 2012, the world allegedly comes to an end at the hands of a human-made virus, ravaging the global populace and leaving only children untouched. It is at this time that vampires emerge from the recesses of the earth, likely followed by age-old horrors of the dark thought only to be myth. The vampires sweep the earth and claim it in a single violent stroke, subjugating the remnants of humanity and leading them beneath the surface to safety. This "protection" comes at the price of donating blood to their captors. At the age of twelve, Yūichirō and his friend and fellow orphan Mikaela plotted to escape along with the children in Hyakuya Orphanage. However, this resulted in their deaths and Mikaela sacrifices himself in order for Yūichirō to escape and be saved by members of the Moon Demon Company, an extermination unit of the Japanese Imperial Demon Army. Four years later, Yūichirō dedicates his life to destroy vampires and seek revenge against them for murdering his "family".

Shiro is an easygoing teenager content with just being a student—until his seemingly perfect life is halted when a bloodthirsty clan, glowing red with fire, attempts to kill him in the streets. Unbeknownst to Shiro, he is suspected of murdering a member of their clan and will need a miracle to escape their vengeance. Miraculously, a young man named Kurou Yatogami swings in and aids Shiro in his getaway, only to reveal he's also after Shiro's life. Now a hunted man, Shiro will have to evade the clans of seven powerful kings and desperately try to prove his innocence—before it’s too late!

Kae Serinuma is a second year high school student and an avid fujoshi who secretly ships her classmates, Igarashi and Nanashima. The death of her favorite anime character causes her to become stressed and lose weight rapidly. Now that Serinuma has become an attractive girl to her classmates, snarky junior Shinomiya and senior Mutsumi, how is she going to deal with them with her constant BL-filled fujoshi mind?