Juken, known alternately as Jyuken or the Carmine (赤の珠献), stands among the Four Kings serving Nyanma, the series’ central antagonist. Initially devoted, she executes missions to destabilize Novel Worlds by planting traps and warping storylines. Her combat arsenal includes summoning endless razor-edged boomerangs, manifesting claws from dark energy, unleashing projectile strikes, and shapeshifting into story characters to infiltrate narratives undetected.

A turning point emerges when exposure to the Eto Rangers’ unbreakable unity sparks doubt in Nyanma’s cause. This fracture deepens as Juken unlocks Chocolat’s sealed memories, uncovering Nyanma’s hidden past and the deceit that reshaped her. Fueled by betrayal, Juken openly challenges Nyanma, denouncing her self-delusion and condemning the lies that bound them.

Her strategic prowess surfaces in missions like *The Bremen Town Musicians* arc, where she manipulates townsfolk and Rangers via a hypnotic keyboard melody, and *The Bluebird of Happiness* arc, where she engineers lethal traps. Even after Nyanma reabsorbs her, Juken’s lingering influence briefly paralyzes her commander—a fleeting act of rebellion defying their rigid hierarchy.

This evolution from unwavering allegiance to critical defiance stems from witnessing genuine camaraderie and confronting Nyanma’s obscured origins. Her arc paints her as a layered adversary torn between loyalty, self-discovery, and the fallout of manipulation.