A female knight travelling to take part in the Holy Knight Selection Tournament. She plans to use the prize money to help her impoverished hometown of Gumi Village, but is injured in an attack by the opposition during her journey and asks Zero to take her place. From then on, she follows Zero's whereabouts and witnesses the battle. Zero's goal is the Platinum Halberd, while Marbet's goal is the prize money, and their interests coincide.

After the battle, as Zeguchi is leaving, she is entrusted with the unusable Thunder Dragon Sword.The reason is unknown.