The main protagonist and the top ace agent of the special defense agency CODE. He possesses an innate lucid dreaming ability, allowing him to freely enter the 'Plaza', the world of human subconsciousness. Breaking away from the childish belt-style transformation devices, he is the official user of the 'Zetz Driver', the first in Kamen Rider history to be worn as a diagonal harness across the chest. By inserting and rotating the 'Capsem', a sphere-shaped exclusive item, into the driver, he transforms into Kamen Rider Zetz, a classic suit featuring a black body and flashing blood-red eyes. After being pushed to the brink of death by a comrade's cruel betrayal, he miraculously returns to the past through a loop (prophetic dream) and wakes up to change the future. Though usually cool-headed and stoic, he is a compelling dark hero who harbors a burning sense of justice and a heavy responsibility to save those trapped in nightmares.

Yorozu Baku's eternal nemesis and the user of 'Kamen Rider Nox', the official second rider of this work who also wears a chest-mounted transformation device. Like Baku, he possesses powerful lucid dreaming abilities, but unlike Baku who seeks to purify nightmares, he harbors the dangerous goal of absorbing and dominating the destructive energy of nightmares into his own suit. His design is characterized by a pitch-black suit with purple accents and red eyes flashing on the chest, and he wields a massive greatsword with heavy, brutal execution. He shows a cunning side by joining forces with the enemy Nightmare faction when necessary, but in reality, he is a thorough individualist who pursues only his own power. As a top-tier rival character with a dark hero style devoid of any childishness, he clashes with the protagonist at every turn.

A mysterious girl existing in the 'Plaza', the dream world created by human subconsciousness and pure desires, and the main heroine of this work. She plays a crucial role in healing the anxious minds of the public wandering through dreams with her singing voice. To prevent real-world humans from falling into eternal nightmares due to the indiscriminate attacks of the Nightmare monsters, she is a key ally who works closely with Yorozu Baku and the secret defense agency CODE. She possesses a powerful prophetic ability to sense signs of nightmares starting or the location of monster appearances, making her an essential navigator for Zetz's battles. Usually bright and cheerful, she provides great strength to Baku, but in the latter half, it is revealed that her very existence is deeply connected to the 'Dream of Terrible Collapse', the final goal of the Nightmares, making her a central figure who drives the tension and heavy narrative to its peak.

The supreme commander of the defense agency 'CODE' who thoroughly deceived Yorozu Baku and drove him into a trap, and the ultimate traitor of this work who fights using mechanical drones. In the beginning, he approached under the mask of a reliable mentor, but in reality, he is a cold-blooded man who does not hesitate to use the young Nemu as a cruel experimental subject for his own goals and the organization's interests. He shows a cowardly and cunning side by hiding in a safe place and remotely controlling the humanoid drone 'Code Zeroid', eventually even ordering the assassination of Baku, who is like a son to him.

A mysterious figure who greets Odaka after he wakes from a nightmare, and the supreme leader of the monster group 'Nightmare'. The Lady was once a top-tier agent of the secret defense agency 'CODE', but she escaped the organization after being unable to endure the nightmares and the side effects of harsh Dream Running. As the main villain of this work, she possesses the bizarre ability to read others' minds and freely control black butterflies. Her final goal is to reconstruct a world where CODE, which used her as a tool, never existed. In the latter half, she stands at the center of the narrative when the shocking secret of her birth as the biological mother of the main heroine Nemu is revealed. Nemu is a manifestation of a being from her dreams into reality, and she cruelly attempts to exploit her daughter despite knowing that Nemu's existence is directly linked to the 'Dream of Terrible Collapse' that will destroy the world. In the late stages of the story, she fuses powerfully with the Phantom Gore Nightmare and others, transforming into a grotesque figure with slashed eyes and showing a desperate, chilling madness.