Also known as: レオ・デモンハート
He is a main character in Yuusha Yamemasu. Leo has Blue Hair / Black Hair, Red Eyes, , Short Hair, and his attire alternates between casual clothing or a black suit of armor used to conceal his identity from Echidna (Yuusha Yamemasu).
It is revealed during the series that Leo is the byproduct of the Demonheart experiment, which has resulted in his unrivaled power and an extended lifespan reaching well beyond 3000 years.