Reiju is a slim young woman with shoulder-length dark pink hair, covering her right eye and curling upwards at the tips. She also has blue eyes, and wears light pink lipstick. Like all the Vinsmoke siblings, she has distinctive curly eyebrows that form a spiral resembling the number "6". However, unlike her brothers Sanji and Yonji, her eyebrows appear to swirl symmetrically in opposing directions. Both of her thighs are tattooed with a number "6", referring to the name of the organization "Germa 66". When commanding the forces of Germa 66, Reiju wears a raid suit, comprising a revealing light pink dress with a split in the center going down to her stomach and her navel, and covered by gold target-shaped symbols—references to the number "0" (Rei) in her name. She also wears dark pink gauntlets, a blue ascot, a pair of black headphones with the number "66" on them, and a patterned purple and black cloak shaped like the wings of a moth. Outside of her raid suit, Reiju has been shown wearing a skinny purple headband in her hair, a short white satiny dress with a frilled neckline and a pink cravat, and dark high heels. For formal functions, she also wears a red, thigh-length royal cape that is clasped in front of her neck. In the Whole Cake Chateau infirmary, Reiju wore a white frilled dress shirt, and a bandage wrapped around her left leg. During the Tea Party, Reiju changed into a short, sleeveless dress with a frilled V-neckline, as well as dark tights that reach halfway up her thighs. She wore a light-colored royal cape draped over a single shoulder. In the anime, her outfit colors are inverted, with her dark shirt being light pink, her thighs are white and her cape is pink. When chaos broke out, she changed back into her raid suit. Unlike her cruel and abusive brothers, Reiju can be kind and empathetic, but this is frequently masked by a cool, callous demeanor due to the militarism of her family and her father's stern disdain for compassion. As a result, Reiju prefers to show kindness only when it will not endanger her own comfort or safety. During her childhood, Reiju would openly laugh at Sanji's misery as he was enduring his brothers' vicious acts of cruelty; however, she confided to Sanji that she only laughed with their brothers to avoid being subjected to similar cruel bullying herself, as she would treat him with care and sympathy when they were not around. Reiju also expressed concern for Sanji when it was said that he had died (but, as usual, she hid her concern behind a smile). She even cried in secret as she listened to their father cast Sanji out of the family, before helping him escape onto the Orbit and encouraging him to find friends on the sea. Her instinct for self-preservation resurfaced when she could not understand why Sanji would return to a home that abuses him, just for the sake of protecting his mentor. However, to this day, Sanji remembers Reiju and their mother as the only members of his family to treat him with any degree of compassion. Reiju's general manner is mild and reserved, and she very rarely reveals her true thoughts and feelings to others. Throughout her life, she has disguised her shame and disdain for her Vinsmoke heritage behind an apparent enjoyment of their luxurious royal lifestyle, and a false respect for their family's historical strength, achievements, and privileges. In truth, however, Reiju's innate sense of morality leads her to believe that her kingdom is nothing but a war machine that the world would be better off without. This view applies especially to her father and brothers (excluding Sanji), but also to herself and her own actions as a mercenary. Like her brother Ichiji, Reiju also prefers to think or muse silently to herself as she watches certain developments unfold, hiding her true thoughts and feelings behind an enigmatic smile. Indeed, the only person to whom she has ever openly expressed her true thoughts and feelings, whether as a child or an adult, is Sanji. Reiju has been shown to possess great intelligence and intuition, as she was the only person (among both her family and the Straw Hats) to suspect that Pudding may not be what she seemed. She has also exhibited a calculating side; for example, she appears to be aware of Sanji's weakness for attractive women, showing him ten beautiful chambermaids that would be at his beck and call in order to convince him to accept his arranged marriage. She also easily charmed the Sanji retrieval team in their first meeting, humiliating Yonji and apologizing for his behavior in order to prevent a confrontation with the Straw Hats. Reiju's occasional actions and manner of speech can be slightly flirtatious. Even before she was properly introduced to Luffy, she unabashedly placed her mouth over his in order to suck out the poison which was festering throughout his body.