Mika is mature,considering and smart due to his hard childhood. As the apocolypse starts and the vampires take over the ruined world. Some vampires killed all the orphange kids mika was living in. Only his best friend Yuu his now only familymember survives and is now in the Vampire Extermination Unit from the Japanese Imperial Demon Army lead by humans. They both are now enymies. As mika got kidnapped by the vampires he was forced to become a vampire and fight with them against humans.