The fourth OVA "Strike the Blood IV" will be released in 6 volumes in 2020, on April 8, June 24, September 30, December 23, March 24, and June 30, 2021. Each volume has 2 chapters, for a total of 12 chapters. The stage of the story is the demon special zone "Enlai Island". The fourth true ancestor who lost his memory is fighting a new battle! ! Under the moonlight, Akatsuki Kojou woke up on the beach, and in front of him was a white-haired girl in monk's clothes. "I finally found you, Akatsuki Kojou. My name is Kasugaya Shizuku Kastiela - I am the one who is responsible for monitoring you." Floating 330 kilometers south of Tokyo, Japan's "only" demon special zone "Enlai Island". Kojou, who has lost all his memories except his name and cannot even summon the fourth true ancestor's beast, what is the cruel mission that he and his new companions will challenge together on the isolated island in the sea! ?