The world's biggest meddler: His catchphrase is "I'll protect the world, even if it costs me my life!" He is an unusually kind and straightforward young man who cannot ignore others in trouble. Self-sacrificial risk-taker: In his pursuit of everyone else's happiness, he is clumsy enough to put his own body and even his memories on the back burner. A family man at heart: He loves his family and their bathhouse, "Happy Spa," more than anything, and that bond is the primary driving force behind his battles. The eldest son of the Igarashi family. Daiji and Sakura call him Ikki-nii.

An ultra-positive mood maker: He always has high energy and a talkative, comical personality, often breaking the fourth wall to speak to the audience. Deep love for Ikki: Initially, he appeared as a typical demon plotting to take over Ikki's body, but as their bond deepened, "protecting Ikki's smile" became his reason for living. Surprisingly devoted: Near the end of the story, he told a heartbreakingly kind lie, acting as a villain to be defeated by Ikki (and thus vanish) in order to restore Ikki's memories. A total show-off. First person: I (Ore-chi). Ikki's demon.

A serious elite with a strong sense of justice: He is talented enough to be chosen as a captain for FENIX (a defense organization) and is a reliable person who thinks seriously about peace. Inferiority complex and fragility (Fall to darkness): Due to a strong complex toward his talented older brother (Ikki) and losing sight of justice in battle, he suffers a serious mental breakdown and becomes an enemy to Ikki and the others mid-to-late story. The demon lurking within, "Kagerou": Born from Daiji's jealousy and distorted sense of justice, Kagerou (Kamen Rider Evil) is a cold, nihilistic cynic—the polar opposite of Daiji. Through conflict and reconciliation with Kagerou, Daiji grows significantly. The second son of the Igarashi family.

Born from Daiji's "darkness (jealousy)": Since he was born from the intense inferiority and jealousy Daiji felt toward Ikki, he was initially a cold-blooded demon who ruthlessly targeted Ikki's life. A dry, nihilistic lone wolf: He maintains a cool attitude, habitually mocking Daiji as a "wimp" or "softie" and showering him with harsh words. He also has a unique side, loving spicy food (especially super-spicy curry). The ultimate tsundere (Daiji's guardian): While he belittles Daiji verbally, his essence is a being that takes on Daiji's "true feelings (weakness)" for him. When Daiji is truly hurt or about to go down the wrong path, he will act as the villain to fire Daiji up, possessing a bond deep enough to risk his life for Daiji's growth. Daiji's demon.

A fighter obsessed with being "invincible": A high-ranking karate practitioner with very high combat ability. Her catchphrase is "Because I'm invincible," and she is strong-willed and tomboyish, never hesitating to speak her mind to her brothers. Actually the most sensitive and prone to tears: Mentally, she is still a high school student. She is bad at admitting her own "weakness" and has a kind, pure heart that cries more than anyone for those who are hurt. Loves the demon "Lovekov": She dotes on Lovekov, the manifestation of her own weakness, with overprotective affection like a mother or older sister. The eldest daughter of the Igarashi family.

A waddling mascot: Though snake-themed, she looks like a stuffed animal and generally only says "Love~." She has almost zero combat ability and a clumsy cuteness, always being protected by Sakura. Actually more mentally mature than Sakura?: Though she is the demon born from Sakura's weakness, she has a dual nature where she suddenly spews fluent insults (sharp-tongued) like "You weakling!" when Sakura is brooding. Sakura's demon.

Normally: A show-off who is high-energy and speaks with mixed English. He loves past Kamen Riders. Essence: At his core, he is a clumsy, lonely person who can't be honest with his feelings. After reconciling, he returns to being a reliable ally who supports his comrades.

The man who protects the world at the cost of his life: Possessing an overwhelming sense of justice, he is a passionate man who will act as a shield for others regardless of what happens to his own life. Ikki's catchphrase "Even if it costs me my life..." was originally Hiromi's words. The strength of a gritty ordinary man: Unlike the genius Karizaki or the Igarashi siblings who master demonic powers, he is an "ordinary person" without special talent. However, he has a gritty coolness, never giving up even when hurt, betrayed, or having his life span drained by his transformation belt (Demons Driver). A kind and reliable senior: He goes missing for a time mid-story, but after returning in the latter half, he becomes a mental pillar (a reliable big brother figure) supporting the mentally cornered Daiji and the Igarashi family with adult compassion.

First half (Evil Queen era): A selfish and mischievous "little devil" who did whatever she wanted. However, she was very lonely deep inside. Second half (After becoming an ally of justice): A serious and strong-willed "older sister" figure who reflects on her past misdeeds and fights for others at the risk of her life.