|“||Your being a Magic Knight is what makes me proud! So continue to be the brother that I'm proud of!||”|
Marie is a young girl with short blonde hair and purple eyes. She wears a purple dress.
Marie was born as the second child of House Adlai. Sometime after her birth, her parents die in an accident, and another noble inherits their wealth and casts out her and her older brother Gauche, who does everything to protect her, killing and stealing as needed. When Gauche is imprisoned, Marie is sent to an orphanage in Nairn.
On her tenth birthday, she is playing with Asta, Marco, and Ruka when Gauche arrives with bags of toys. Jealous, Gauche stomps on Asta, and Marie tells him to stop and declares that Asta will be her husband, which shatters Gauche and angers him more. Sister Theresa then arrives to collect Marie, and after Theresa and Gauche trade insults, Marie leaves with her.
Later that night, snow covers the town and enchants many of the children, including Marie, and they wander out of the town. When they reach the caves, Neige happily greets them, but Marie, who is freed from the spell's control, tells him that friends do not control each other like puppets. Losing his temper, Neige hits her, but Baro stops him and checks the children's mana, noticing that Marie has the most.
After several of the children are drained of their mana, Marie is selected and Neige starts dragging her to the machine. Gauche then arrives and, seeing his sister's injured cheek, fires a light beam at Neige. After Asta and Theresa arrive, the Sister gathers the children together and heals them. As Gauche kicks the defeated Neige, Marie pleads for him to stop but he refuses.
Gauche grabs Marie and flies away after Sally arrives and turns Baro into a monster. Marie demands that they go back, but Gauche refuses because he would not be able to protect her. She punches him and tells him that she hates when he is like this, and that she likes him for being a Magic Knight who protects others. They encounter Marco at the cave entrance, and Gauche leaves Marie in his care.
Finral Roulacase transports the injured and the children back to Nairn, where Marie stands next to her brother and watches as healers take care of Theresa. After Theresa passes her remaining mana to Gauche, Marie offers hers, too.
After the battle, Gauche visits Theresa, who is still recovering, and Marie has to tell them to stop fighting. She then cheers as Asta arrives, which angers her brother. After Rebecca kisses Asta, Marie wants to kiss him as well, so Gauche tries to kill the boy.
- Magic Power: Marie has more mana than other children her age, but it is not fully developed, meaning she can easily be placed under even weak enchantments.
- Mirror: Marie carries with her one of her brother's mirrors. It is usually used as communication device, allowing her to see and talk to her brother, but could also be used to track her location or protect her from enchantment.
- "Your being a Magic Knight is what makes me proud! So continue to be the brother that I'm proud of!" 「お兄ちゃんが魔法騎士団なの私の自慢なの...! 私の自慢のカッコイイお兄ちゃんでいて...! "Onīchan ga mahō kishi-dan'na no watashi no jiman'na no...! Watashi no jiman no kakkoī onīchan de ite... !"」
- Marie's favorite things are her older brother, everyone at the church, and stuffed toys.