Kamen Rider Arsène / Kouki Saionji Age: 25 Gender: Male Public Face: An aristocrat of the restored Saionji family. An entrepreneur running a redevelopment project for the slums. Personality: An elegant and flamboyant gentleman. He often flirts with women but holds a firm belief in respecting them. He is highly intelligent and has a talent for business management. Phantom Thief Activities: He sends advance notices and steals jewels with flair. He detests the misuse of Calamity Jewels and prioritizes their recovery. His ultimate goal is the legendary jewel, the Luna Drop. Transformed Appearance: Metallic red armor with sapphire blue compound eyes. An armor design reminiscent of Rococo-style aristocratic formal wear. He transforms into Kamen Rider Arsène using the Trigger Driver and a Calamity Jewel. His finishing moves are the Rider Kick "Phantom Finale," the gunshot "Calamity Bullet," and the slash "Calamity Slash." Weapons: Jewel Trigger, knife-type weapon Jewel Reaper. His catchphrase is "Let us bring tonight's curtain down."

Rei Shikimori Age: 25 Transformed: Kamen Rider Sherlock Transformed Appearance: Metallic blue and white armor. Compound eyes are ruby red. A design reminiscent of Sherlock Holmes. Personality: Calm, collected, and polite, speaking to everyone in formal language. He excels in reasoning and martial arts but is so serious that he lacks flexibility. Transformation Item: Trigger Driver. He developed two units himself, but one was stolen by Arsène. Weapon: Jewel Trigger. A gun-type weapon used by removing it from the belt. Finishing Moves: ・Calamity Bullet: A finishing shot that consumes a Jewel. ・Detective Finale: A Rider Kick that focuses the power of the Jewel. Purpose: To solve the mystery of the Calamity Jewels and defeat the monster Calamity. He pursues Arsène to recover the stolen belt. While suspecting Salon Noir, he accepts their requests to conduct his own investigation. He does not know Arsène's true identity.

Rin Kujo Age: 24 Gender: Female Position: The sole subordinate and personal maid of the Saionji family. A classical maid who combines a cute appearance with a brilliant mind and versatile domestic talents. A capable individual who is quick-witted and handles situational judgment, information gathering, and mission support with ease. She never drops her formal tone with Kouki, showing him respect as her master. On the other hand, she is completely unfazed by Kouki's sweet pick-up lines or flamboyant behavior, calmly brushing them off. She knows Kouki's personality and behavior patterns inside out, often making necessary preparations in advance. As the only subordinate Kouki employs, she is a vital presence supporting the activities of the Phantom Thief Arsène from the shadows.

Grotesque monsters created by the power of Calamity Jewels. When humans are affected by a Calamity Jewel, they transform into non-human forms. They become dangerous beings with such high ferocity that they lose their reason and indiscriminately attack people around them. Their appearance and abilities after transformation vary depending on the Calamity Jewel used. The existence of Calamity, which turns humans into monsters, symbolizes the danger inherent in the Calamity Jewels. Their personalities differ based on the will of the original human.

Noir Gender: Male Age: Unknown (rejuvenated by the power of a Calamity Jewel) Position: Leader of the secret society "Salon Noir" / User of Kamen Rider Noir The absolute leader of the secret society "Salon Noir," which unites the world's leading billionaires. Publicly active as a jeweler, he manipulates plans using Calamity Jewels behind the scenes. He is the only person who knows the relationship between the Calamity Jewels and the legendary jewel "Tears of the Moon." He rarely appears on the public stage, using Calamity as proxies to hide his own power and objectives. He murdered the parents of Shizuku Tsukishiro, the heir to the Tears of the Moon, and plots to exploit her while she remains ignorant of the jewel's secrets. His true identity is the final boss symbolizing jewels and ruin, Kamen Rider Noir. He transforms using a special dedicated jewel, drawing out the power of the Calamity Jewels to the limit. Upon transformation, he enters his final form immediately, standing before Arsène and Sherlock with an elegant, stylish appearance and overwhelming power. Transformed Appearance: Onyx black armor with amethyst compound eyes, accented with gold decorations. Details of his transformation item, the name of his dedicated jewel, and his true purpose remain shrouded in mystery.

Shizuku Tsukishiro Age: 20 Gender: Female Position: Daughter of the Tsukishiro family / Successor of the "Tears of the Moon" The daughter of the prestigious Tsukishiro family, which has passed down the legendary jewel "Tears of the Moon" (Luna Drop) for generations. A beautiful woman full of grace, she is highly dignified and possesses great pride. While she has a stubborn side, she has a strong sense of responsibility as a member of a noble house. She treasures the Tears of the Moon as an irreplaceable family heirloom and knows it is a legendary treasure. However, she is unaware of the true secret hidden within the jewel or its connection to the Calamity Jewels. Normally, she would have been taught the family's secrets and mission by her parents. However, her parents were murdered by Noir, the leader of the secret society "Salon Noir." Shizuku inherited the Tears of the Moon without ever knowing the truth. Noir plots to exploit Shizuku, who is ignorant of the jewel's secret. However, Shizuku does not know that Noir is her parents' killer, nor does she know his true purpose. Eventually, she becomes embroiled in the incidents surrounding the Phantom Thief Arsène, the Detective Sherlock, and the Calamity Jewels. When she learns the truth hidden in the jewel she inherited, she will have to face her own destiny.