The fourth Rozen Maiden doll, and Suiseiseki's tomboyish twin sister. As with Suiseiseki, she is a gardener that has the power to enter human dreams, and carries a set of pruning shears that she uses to tend humans' soul trees. She wields these in battle combined with acrobatic flight, her spirit Lempika and her hat which can be thrown and returns like a boomerang, a tactic she used to temporarily disarm Shinku in their second fight. She also has heterochromatic eyes like Suiseiseki, but the colors are the mirror image of her sister's. Her personality is also the polar opposite of Suiseiseki; she is rational, calm, quiet and deeply devoted to her master and to her duties, including the Alice Game. She possesses a sharpness in her speech that is similar to Shinku's, attacks ruthlessly in combat, and does not tolerate sub-par actions. Her appearance is not only the most masculine of the dolls, but her speech is also noted to be of the masculine form, using the first person pronoun "boku" instead of gender neutral pronouns like "jibun" or "watashi." Souseiseki's presence is much more significant in the anime than in the manga.

In the manga, her master wanted to use Souseiseki's power to enter other people's dreams and exact revenge on his brother's lover, who he felt had stolen his brother from him. Since Souseiseki alone could not achieve this goal, she fights Suiseiseki to gather the two gardeners' tools, the shears of the Gardener and the watering can of the Gardener, which together can affect an individual's soul tree. She eventually realizes that it is her master's heart that needs to be freed and sacrifices herself to do.

In the anime, Souseiseki is devoted to a lonesome old man, who uses her as a substitute for his deceased son, Kazuki. She is shown to be slightly more eager, probably from a sense of duty, to participate in the Alice Game than her sisters. In the OVA, she is introduced in the flashback in mid-fight with Shinku and later does not hold back in attacking a then-harmless Suigintou. Throughout Rozen Maiden träumend, she questions her idyllic lifestyle, and much to Suiseiseki's disappointment, takes part in the Alice Game out of devotion to Rozen, to fulfill his wish of finding Alice and relieve his perceived grief.

Her artificial spirit is named for a fragrance by Lolita Lempicka. Souseiseki was also the first runner-up for Saimoe 2005.

Medium: Shibasaki Motoharu (Anime) / Yuibishi Kazuha (Manga)/Jun Sakurada (alternate dimension, manga)/ Jun Sakurada (real one. This is because the alternate Jun transfered the ring to the younger Jun because Souseiseki can't stay in the not wound world. Manga.)

Artificial Spirit: Lempicka