On the surface, Satō Matsuzaka presents herself as a kind, composed, and dependable girl. She is well-liked by those around her, admired by her co-workers at the café where she works, and seen as friendly and capable in any situation. Her classmate and friend, Shōko Hida, notes that Satō has had several stalkers in the past, a testament to her popularity. At school, Satō is perceived as practical, well-educated, and supportive, often lifting the spirits of those around her.

However, this outward charm conceals a far darker nature. Satō is manipulative and willing to deceive, exploit, or even kill to protect her life with Shio Kōbe, whom she views as the embodiment of true love. She becomes unhinged when she perceives a threat to her relationship with Shio, as seen in her willingness to murder those she deems dangerous, including the apartment’s previous owner and, reluctantly, her friend Shōko. While she prefers to use careful planning and social manipulation such as how she dealt with Sumire Miyazaki Satō does not hesitate to resort to violence when necessary. Although she occasionally shows flashes of guilt, such as when she hesitates before killing Shōko, she ultimately justifies her actions as necessary for protecting her “sugar happiness.”

Satō often rationalizes her behavior by citing the influence of her abusive aunt, using this as a way to cope with her guilt and self-doubt. Her obsessive and dangerous devotion to Shio reflects characteristics commonly associated with the yandere archetype, as she seeks to isolate their world from what she views as a corrupt and tainted society.

Satō Matsuzaka is a strikingly beautiful girl with fair skin and long, light bubblegum-pink hair that reaches down to her thighs. She typically styles her hair into small buns on either side of her head, with the left bun adorned by white lace and a red plaid ribbon. Her large, dark crimson eyes contribute to her soft and innocent outward appearance, enhancing the contrast with her darker inner nature.

Satō’s school uniform consists of a brown vest fastened with two golden buttons, worn over a navy blue blazer and paired with a green skirt. She completes the look with black knee-high socks and brown shoes. Although her wardrobe varies at times, this uniform is her most common attire.

She is often seen carrying a blue bag decorated with imitation sweets. Hidden inside are tools she keeps close at hand for protection or, when necessary, for committing violent acts including a taser, a knife, and other items she uses to defend her “happy sugar life.”

Satō Matsuzaka’s tragic past plays a central role in shaping her obsessive and destructive worldview. Orphaned at a young age following the death of her parents in an unspecified accident, she was placed in the care of her abusive aunt. Her aunt exposed Satō to twisted and harmful notions of love, subjecting her to emotional, physical, and implied sexual abuse under the guise of teaching her about the “many forms of love.” This upbringing left Satō with warped ethics and a desperate longing for a singular, pure love, rejecting the idea of loving everyone equally.

In her search for that one special person, Satō engaged in numerous empty relationships, seeking fulfillment through casual encounters that left her bitter and detached. Everything changed when she met Shio Kōbe, a young girl she came to see as her salvation and the embodiment of true love. Determined to protect their life together at any cost, Satō resorted to manipulation, blackmail, and murder including killing the apartment’s previous owner and later her own friend, Shōko Hida, to safeguard her secret.

Throughout her story, Satō’s actions grow increasingly desperate as she attempts to cover her crimes and maintain her “happy sugar life” with Shio. This culminates in her plan to fake her death and flee with Shio. In the end, cornered on a rooftop and with no escape, Satō and Shio leap together. In that final moment, Satō experiences genuine selflessness, shielding Shio from the impact and dying upon hitting the ground.

Shio Kōbe
Shio is the object of Satō’s obsessive love, whom she refers to as her “sugar love.” They first met when Satō found Shio abandoned in an alleyway. From that moment, Satō resolved to protect their life together at any cost. She keeps Shio confined in their apartment, which she calls their “castle,” locking the door to prevent Shio from leaving and potentially exposing their secret. Satō views her feelings for Shio as pure and sweet, in stark contrast to the emptiness she experienced in past relationships.

Shōko Hida
Shōko was Satō’s best friend and confidante, and the two shared a close bond. However, this trust was shattered after Shōko hesitated to affirm their friendship following an encounter with Satō’s aunt, and later when Shōko took a photo of Satō and Shio together. Fearing exposure, Satō killed Shōko by slitting her throat. Rather than disposing of the body, Satō cleaned and dressed Shōko in her own uniform, leaving her in the apartment to perish in the planned fire.

Asahi Kōbe
Satō sees Asahi as a direct threat to her life with Shio and is determined to keep him away. She nearly attacked him with a crowbar during a confrontation at the café. Asahi, in turn, views Satō as the person responsible for destroying his family and for Shōko’s death, fueling his determination to confront her.

Taiyō Mitsuboshi
Satō initially befriends Taiyō at work, and while he confesses his feelings for her, she rejects him. She later rescues him from their abusive manager. However, upon realizing Taiyō’s fixation on Shio as a symbol of purity, Satō begins to see him only as a tool, exploiting his obsession to manipulate him into helping keep Asahi away from Shio.

Sumire Miyazaki
Sumire admires and idolizes Satō, aspiring to be like her in both appearance and manner. Satō manipulates Sumire’s affection, falsely claiming to love her to prevent Sumire from prying into her private life. Sumire ultimately provides Satō and Shio with passports to aid their escape. After Satō’s death, Sumire is devastated upon learning of it through a television broadcast.