Mirei Shikishima is the protagonist of Valkyrie Drive Mermaid, and is Mamori's Liberator. She is a young girl who possesses an outstanding figure with tan skin and blond hair long enough to touch the ground. Due to her extremely reserved appearance, people think that she's a scary person but in reality, Mirei is a pure-hearted innocent person. Courageous and energetic, she doesn't avert her eyes from disturbing scenes. Still, she is fond of cute things. As a Liberator, her power is S-Class. Because of her reserved nature, only few people are aware of her past.