Mirei Minae is the current head of the Minae family and the leader of Team Daybreak. She is the estranged younger sister of Danji Momoyama, whose real name is Nadatsugu Minae. For much of her life, Mirei was led to believe by her family that her brother had died, a lie that caused her significant emotional trauma and left her feeling abandoned and isolated. She is a young woman who has been blind from birth, a condition that has profoundly shaped her life and her approach to cardfighting.

To the public, Mirei projects a cheerful, lively, and helpful personality, which has earned her an idol-like popularity as a Vanguard fighter. However, this outward demeanor is largely a facade. In reality, she harbors deep-seated feelings of loneliness, an inferiority complex regarding her blindness, and intense pressure to succeed as the heir of her prestigious family and leader of her team. She internalized the metaphor of a king from a childhood picture book, believing a leader must always be strong, bear every burden alone, and make all sacrifices for the sake of their kingdom or team, regardless of their own desires. This pressure often causes her to misinterpret the actions and laughter of others as mockery or pity directed at her, and she can react with anger or distress when she feels patronized. Her emotional state is particularly volatile in noisy environments, where her enhanced hearing can become overwhelmed, leading to panic and hyperventilation.

Mirei’s primary motivation throughout her story arc is to find a place where she belongs and people she can trust, a quest made difficult by the lies surrounding her brother's disappearance. After discovering that Danji is alive, she struggles with feelings of betrayal and demands he abandon his life and identity to stay with her. Her role in the narrative evolves from a primary antagonist to a supporting character. A pivotal moment in her development is a cardfight against Yu-yu Kondo atop Nagoya Castle. In this match, she realizes that her self-perception as a solitary king was a lie; she does not have to fight for everyone else's sake but can fight alongside them and simply have fun. This loss, and Yu-yu's earnest friendship, helps her shed her burdensome persona and begin to heal. By the time of the Deluxe tournament, Mirei has shown significant emotional growth, having overcome much of the intense anguish that once drove her actions, though she remains a fierce competitor.

Mirei is an exceptionally talented cardfighter who has memorized every card in the game to compensate for her blindness. She uses card sleeves with textured stickers, allowing her to identify each card by touch. During a match, she relies on an assistant to narrate her opponent's plays and indicate card placements on the field, while she uses her highly developed sense of hearing to track the flow of the game. Her fighting style originally utilized a Trickstar deck, but she switched to a Dragon Empire deck focused on the Armed mechanic after her brother left the family. Her primary ace unit is Sealed Blaze Maiden, Bavsargra, which she later upgrades to Sealed Blaze of Arbitration, Bavsargra Aksayya for the third Deluxe tournament. This deck revolves around equipping various weapons to her vanguard, a strategic approach that complements her perfect memory and ability to adapt to any situation. Within the Deluxe tournament, she competes fiercely, demonstrating her continued high-level skill and advancing to the quarterfinals. Her key relationships, beyond her complex bond with her brother Danji, include her friendship with Yu-yu Kondo, who helped her change her worldview, and her role as a mentor to Urara Haneyama.