Suigintou is the first doll of the Rozen Maiden collection. Her desire to win the Alice Game is the strongest of all the dolls, and is primarily driven by her wish to gain the attention of "Father" (Rozen). Sadistic, spiteful, and arrogant (all due to her spectacular Superiority complex), Suigintou has no inhibitions when it comes to the Alice Game. She will use any method available to her, regardless of how brutal they may be, to grasp victory. Although she generally avoids associating with the other dolls on a social level, she has a particularly strong hate for Shinku. This hate borders on obsession, as she can approximate how many hours and minutes since they have last met. However, upon meeting Megu, her medium, Suigintou's attitude and motivations begin to shift; she begins to feel a strong affection for someone other than "Father". Suigintou's desire to protect Megu begins to even overpower her wish to meet him: she hopes to use the collected Rosa Mystica to heal Megu of her heart ailment, rather than become Alice.

Suigintou has a number of unique traits and flaws amongst the seven Rozen Maiden. In the anime, she is missing her torso; Shinku explains at one point that before Suigintou was completed, her design was erased, but gives no further explanation as to why or how. Curiously, after Suigintou is destroyed in battle by Shinku partly she is restored mid-way through Rozen Maiden Träumend. The identity of the person responsible for her restoration is never revealed. In the Rozen Maiden Träumend finale, she tells Shinku that "Father" had told her that even with her flawed body, she was also entitled to a part in the Alice Game. Later, Rozen is seen lovingly fixing her neck ribbon as she is unconscious. He even grips gently around the waist afterwards, implying that he has mended her incomplete body.

Along with her artificial spirit, Meimei, Suigintou's weapons are her ragged black wings. With their arrow-like feathers, she can conjure up a shield, a large sword, or even twin black dragons. Suigintou can also create destructive blue flames as a last resort in battle. The variety in Suigintou's abilities, particularly when combined with her savagely cunning nature, make her a strong player in the Alice Game.

It is noted that "Mei" in Japanese means darkness.

Medium: None (First Season)/Megu (Second Season)

Suigintou's name in English means, "Mercury Lamp".