Yuuichirou Hyakuya wants revenge on the vampires who slaughtered the children he regarded as family. Years after escaping captivity, he serves in the Japanese Imperial Demon Army, determined to fight those who once held him prisoner.
His captivity began after a mysterious virus killed everyone older than 13. Previously hidden vampires emerged, enslaving humanity's survivors and demanding blood in return for protection. Yuuichirou, Mikaela Hyakuya and the other children from their orphanage were taken captive together. Unwilling to accept the vampires' brutal rule, Mikaela devised an escape plan, but the attempt ended in disaster. Only Yuuichirou made it out, and he was found by the Moon Demon Company, a military unit devoted to exterminating vampires in Japan. His resolve to avenge his family now drives him, though the cost remains uncertain.
