The story revolves around two brothers whose home had been destroyed by vampires. They were separated, each believing the other to be dead, until they finally meet again years later.
But now they face a new problem: while the younger brother, Yuliy, became a vampire hunter to avenge the loss of their family, his brother Mikhail got turned into a vampire himself. What must they do in this situation, and what is the mysterious relic called "The Ark of Sirius" that the vampires are after?
Based on the original anime television series of the same name produced by P.A.Works in 2018, directed by Masahiro Andou and written by Keigo Koyanagi.