HELLSING OVA originated from the manga drawn by Kota Hirano, which was serialized in the "Young King Hours" magazine by Shonen Gahosha from issue 27 (released May 2, 1997) to November 2008. After the TV series, the OVA series was produced in 2005 as a compliant version of the original. In the US, the original manga was translated into English and published in 7 volumes since 2003, and in 2006, it was nominated for the Best Graphic Novels category in "The Best Book for Readers" at the "Quill Award" which was held in collaboration with major publishing companies and NBC. In 2006 it was also selected as one of the "100 selections of Japanese media art, manga category".

Royal Order of Protestant Knights, commonly known as the "Hellsing", is an organization that secretly protects the British Empire from inexplicable attacks by Midian. Hellsing is led by Integra; protected by Walter, the butler who is one of the few special affairs agencies, and yet the biggest weapon is the Alucard, a real vampire that has been tamed by the Hellsing family for generations. One day, Alucard whimsically turns Seras Victoria into a vampire and invites her to the organization. In the meantime, unlike the past cases that have happened around the world, cases of artificially created vampires are increasing. The Vatican's special agency Iscariot, which opposes the Hellsing organization, also moves to intimidate the Anglican Church at the same time as the situation is elucidated, but behind it is the last ghost of the Nazis who once wrenched the battlefield, the Major. He leads a battalion, the Millennium. An army of 1,000 vampires, and the 9th Aerial Mobile Crusade of 3,000 people. An unprecedented "fight" with the worst real vampire, Alucard. There is only one command, search and destroy!!