Maria Naruse is a significant character in the anime series 'Shinmai Maou no Testament' (The Testament of Sister New Devil). She is a succubus and serves as the younger sister of Mio Naruse, the primary female protagonist. Maria is known for her playful and mischievous personality, often teasing others with a flirtatious demeanor. Despite her young appearance, she is quite intelligent and uses her powers to aid Mio and the protagonist, Basara Toujou. Her role in the series involves providing comic relief, strategic support, and deepening the storyline with her backstory and abilities.