The third Rozen Maiden doll, and Souseiseki's older twin, they are both referred to as "gardeners" for their ability to communicate and tend not only to regular plants, but also to the "soul trees" of humans. Their artificial spirits also allow them to access the dream worlds where such trees are located. Suiseiseki must call upon her artificial spirit to summon her watering can which she uses to nourish the "soul trees" and to launch her plant attacks. She makes an impression with her high-pitched voice, heterochromatic eyes (her left eye is green and her right eye is red), and frequent use of the sentence-ending copula "desu". She is described by Shinku as "the most timid and shy of the sisters" in the first season and even as a crybaby in Ouvertüre. She is quite easily scared of strange noises, and prefers to hide behind her sisters in the presence of strangers. With those she is acquainted however, she shows a very devious personality. Suiseiseki adores the spotlight, and her favorite activities include smashing the window of Jun's room (hitting Jun in the process frequently), picking mercilessly on Hinaichigo, and cackling maniacally. She has a wild imagination, a short temper and a fondness for telling wild lies to terrify Hinaichigo, whom she calls either "chibi-chibi" (tiny tiny) or "chibi-ichigo" (tiny strawberry). For the most part, Suiseiseki and Jun seem incapable of being civil with each other; she refuses to call Jun by name, opting for "runt" ("chibi-ningen," which translates to "little human") instead.

Despite her attitude towards Jun, she does care a great deal for him, and her attempts to cover that up usually manifest in the form of more insults. In Rozen Maiden träumend, Suiseiseki stands out among the dolls in that she values her sisters' love more than the goal of becoming Alice. She is one of the few dolls who opposes the Alice Game, and has no intentions of becoming Alice if it means taking her fellow sisters' Rosa Mystica. Suiseiseki and Jun attempt, without much success, to convince the other Rozen Maidens that the Alice Game is a meaningless endeavor. In her brief appearance in the OVA, she makes the same appeal to her twin several times.

Suiseiseki tries to avoid participating in the Alice Game as much as possible, but she can use her watering can to make plants emerge from the ground and manipulate them. Her artificial spirit is named after the popular Anna Sui perfume. Suiseiseki was also the winner for Saimoe 2006.

Medium: None (First Season)/Jun (Second Season) Artificial Spirit: Sui Dream ("Sui" can mean Amethyst or Jade; called "Sweet Dream" in Tokyopop translation.)

Suiseiseki's name in English means, "Jade Stone."