Suiseiseki is the third doll of the Rozen Maiden series, created by the genius doll maker Rozen. She is the older twin sister of the fourth doll, Souseiseki. Physically, Suiseiseki is distinguished by her long brown hair and her mismatched eyes, with a red right eye and a green left eye, the reverse of her sister's. She typically wears a green dress and a white bonnet. Her speech is marked by a unique verbal tic, often ending her sentences with the copula "desu," which has become a recognizable trait.

In terms of personality, Suiseiseki presents a complex and often contradictory facade. Initially, she can appear shy and nervous around strangers, but this quickly gives way to a much more mischievous and sharp-tongued nature. She is known for being a devious tease, frequently engaging in playful abuse towards her human companion Jun, whom she derisively calls "runt", and terrorizing her younger sister, Hinaichigo, with wild stories. Despite this often mean-spirited exterior, Suiseiseki is not genuinely malicious. Her troublesome behavior masks a deep capacity for care and loyalty. Unlike many of her sisters, she harbors a strong aversion to violence and conflict, particularly the Alice Game, the very purpose for which they were created.

Motivation is a key element of Suiseiseki's character. The Alice Game requires the Rozen Maidens to fight and take each other's Rosa Mystica, the source of their life, to become the perfect girl, Alice. Suiseiseki rejects this entire premise outright. Her primary motivation is not to become Alice but to preserve the bonds she shares with her sisters. She values their love and companionship far above any wish of their creator, Rozen. This places her in direct opposition to the game's core directive and leads to much of the story's conflict, particularly with her twin, Souseiseki, who feels a stronger sense of duty to participate.

The most significant relationship in Suiseiseki's life is with her twin sister, Souseiseki. They are inseparable, having been together since their creation and often sharing the same human master. Their bond is the deepest among the sisters, but it is also fraught with tension due to their opposing views on the Alice Game. While Suiseiseki is fiercely protective and would refuse to fight her sister under any circumstances, she envies Souseiseki's strength and independence. In the manga, this conflict of beliefs leads to a tragic separation, as Souseiseki believes in following their father's will even if it means confronting her sister, while Suiseiseki clings to their relationship above all else. Despite these clashes, her love for Souseiseki remains absolute. She cannot bear to be apart from her for long, and her greatest fear is losing her to the game.

Outside of her relationship with her twin, Suiseiseki forms a crucial bond with Jun Sakurada, a withdrawn boy who becomes her master. Their relationship begins as a series of arguments and insults, with Suiseiseki constantly belittling him. However, as Jun proves his willingness to protect her and risk his own safety for the dolls, she grows to genuinely care for him. She eventually accepts him as her medium, sharing a master with Shinku, another principal doll. Suiseiseki struggles to express her affection openly, so her care for Jun often continues to manifest as teasing and insults, a tsundere-like dynamic. She also interacts frequently with the other dolls, often cruelly teasing Hinaichigo and engaging in rivalry with Shinku, while maintaining a cooperative, if begrudging, alliance with them against common threats.

Within the story's narrative, Suiseiseki acts as a key emotional anchor and a dissenting voice against the predetermined fate of the Alice Game. She often serves as comic relief with her playful schemes and verbal tics, but this lightheartedness contrasts sharply with the series' darker themes. In the original anime, her refusal to fight makes her a target, and she ultimately surrenders her artificial spirit to protect Jun and her sister, rendering herself unable to battle. In the manga, she and Souseiseki's divergent paths over the game lead to a direct confrontation, culminating in Souseiseki sacrificing herself and giving her Rosa Mystica to Suiseiseki, a moment that powerfully illustrates the tragedy of their situation. In later narratives, such as Rozen Maiden: Zurückspulen, Suiseiseki is shown willingly giving up her own Rosa Mystica to revive Souseiseki, a full-circle act that reaffirms her core motivation: kinship is more important than victory or the approval of their father.

As a Rozen Maiden, Suiseiseki possesses several notable abilities. Her primary weapon is a gardener's watering can. In combat, she can spray water from this can to rapidly grow and control massive vines, which can be used to attack opponents, block their vision, or restrain their movements. Her most significant power, however, is her role as a "Dream Gardener," an ability she shares exclusively with her twin. She has the power to find the hidden entrance to a person's inner world, or "dream," and enter it. Inside this mental landscape exists a "soul tree" that represents a person's heart and mind. By using her watering can on this tree, Suiseiseki can nourish it, which in turn allows the person's heart and mind to grow positively. Conversely, she can also overwater the tree, causing its roots to rot and effectively trapping the person's mind in a prison of their own memories. Critically, this power over the soul is incomplete. Suiseiseki alone cannot fully heal or fully destroy a soul tree; she can only affect half of it. To truly change a person's nature, she requires Souseiseki, who wields the complementary gardener's shears to prune away harmful elements. Together, their abilities as twin gardeners create a complete, powerful force over the human psyche.