Zero no Dai Kenja: Wakagaetta Saikyou Kenja wa Shoutai wo Kakushite Nariagaru
ゼロの大賢者 ～若返った最強賢者は正体を隠して成り上がる～
A former grand hero named Siegfried is stripped of his rank, reputation, and abilities by his trusted ally Gilbald and exiled to a dangerous forest. There, he meets a dying vampire girl and sacrifices his blood to save her, transforming into a vampire himself and regaining immense magical power. Reborn as "Zero," he teams up with the girl to seek revenge against Gilbald. His return draws the attention of former heroes from a past great war, who are now forced to confront him.