Mujina serves as a member of the Kaiju Eugenicists, an organization manipulating kaiju for its own ends. Originating 5000 years in the past, she belonged to a group, including Gauma, who brought prosperity to a nation through their kaiju-controlling powers, earning them the title "dragon controllers." This era ended in mutual betrayal: the country betrayed the Eugenicists while they simultaneously betrayed it. Gauma, shifting his loyalty to the princess, killed his comrades, Mujina among them, resulting in her death and Gauma receiving facial scars. Revived alongside the other Eugenicists in the modern day, they now view Gauma as a traitor for piloting Dynazenon against their kaiju. Physically, Mujina is a stoic woman standing 175 cm tall and weighing 66 kilograms. Her attire consists of a white major's uniform, blue pants, white gloves, and white boots. Her personality exhibits a profound, admitted lack of personal ambition, possessing no goals or direction. She routinely defers to the choices of her fellow Kaiju Eugenicists. This aimlessness draws her to identify with Koyomi Yamanaka, whom she encounters intoxicated at a convenience store, observing their shared emptiness regarding desires. Later, exploiting his drunken state, she steals the Dynastriker after giving him her umbrella. This theft forces Gauma and Koyomi to reclaim it, leading to a confrontation where Gauma nearly crushes Mujina and her comrades. Despite the opportunity, Mujina fails to acknowledge her role, instead developing envy and misplaced hatred toward Koyomi. This hardens her resolve, aligning her more ruthlessly with the Eugenicists' cause—a shift surprising even her comrade Onija. Paradoxically, she finds enjoyment in mundane activities like visiting water parks, game centers, soda joints, and watching movies with her comrades. Mujina possesses the ability of "Instance Domination," enabling her to subjugate kaiju and induce their growth to gigantic size. She specializes in controlling four-legged kaiju like Didoras and Bullbind (the latter jointly with Onija). Later, she assists the other Kaiju Eugenicists in controlling Gagula. Her story arc sees her briefly leave the group after Garnix's defeat, seeking purpose. She ultimately rejoins the Kaiju Eugenicists to use Instance Domination on Gagula. Discovering Sizumu inside Gagula, they deliberately allow themselves to be devoured, empowering its second form. Despite this sacrifice, Gagula is defeated by Gridknight and Dynarex, resulting in Mujina's destruction alongside the kaiju. Her name derives from the Japanese folklore term for a badger, referencing the proverb "同じ穴の狢" (a badger in the same cave), implying a connection to wrongdoing despite outward appearances.