Yoshino appears as a petite girl of around 13 to 14 years old, with long, wavy blue hair and gentle blue eyes. She stands at 144 cm, with measurements listed as B73/W55/H78. Her Astral Dress takes the form of an oversized, rabbit-themed green raincoat, featuring a fluffy tail with a pink ribbon attached to the coattail and long rabbit ears on the hood. The coat is trimmed with a gold zigzag pattern, accented with white frills, and has partially detached sleeves at the upper arms. She pairs it with matching green boots worn over pink socks. Beneath the coat, Yoshino wears a simple white dress and a pink ribbon tied around her neck.

After having her powers sealed, Yoshino is often seen wearing a hat. During the summer, she dons a one-piece dress paired with a sunhat given to her by Reine Murasame. Upon enrolling at Raizen High School, she wears the school’s female uniform, similar to Kotori Itsuka’s white sailor-style outfit, before later adopting the standard female Raizen student uniform.

In concept art for her Inverse Form, Yoshino’s hair is depicted as a translucent white. She wears a black variation of her Spirit raincoat with sharper, more pronounced rabbit ears, along with a short drape-like garment covering her chest. This form includes an eyepatch over her left eye, while her right eye turns red. Her left arm’s Yoshinon puppet is replaced with Yoshinon Junior, a smaller and altered version of her original puppet.

Yoshino is portrayed as a shy, gentle, and soft-spoken young girl who is notably more passive than most other Spirits. She avoids confrontation whenever possible, refraining from fighting back even when repeatedly targeted by the Anti-Spirit Team (AST). During her initial appearance, she was so withdrawn that she struggled to speak in full sentences or express herself, relying instead on her hand puppet, Yoshinon, to act as her alter ego and communicate on her behalf. While this coping mechanism was unhealthy, it provided her with a measure of emotional stability. However, when separated from Yoshinon, she would become visibly distressed and, in rare cases, willing to use force to recover her puppet.

Like other Spirits, Yoshino’s emotional state influences her abilities. Upon her debut, her sadness and isolation manifested as persistent rainfall wherever she appeared. Similarly, when Yoshinon was absent, her instability caused her powers to freeze the surrounding environment unintentionally.

After Shido sealed her powers, Yoshino gradually improved her communication skills and began integrating into human society. She soon became capable of holding conversations without relying on Yoshinon and grew more confident and outgoing, particularly after forming a friendship with Natsumi. Her development became most apparent during the Spirit battle royal, where the possibility of losing Shido motivated her to fight with full determination against her fellow Spirits. Ultimately, her growth culminated in a decisive moment when she removed Yoshinon of her own accord and openly confessed her feelings to Shido.

Twenty-six years before regaining her memories, Yoshino was a frail child raised by her widowed mother, Nagisa Himekawa. Due to chronic illness, she spent most of her life confined to a hospital room, with the narrow space and its small window comprising the entirety of her world. One day, Nagisa gave her a rabbit hand puppet, which she named Yoshinon, as a token to remind her that her mother was always watching over her, even when work kept her away. Yoshino planned to make a smaller “junior” puppet representing herself as a gift to her mother.

Tragedy struck when Nagisa died in a work-related accident. Devastated by her mother’s absence, Yoshino’s health deteriorated further, leaving her struggling to breathe. At this point, Mio Takamiya appeared and offered her a Sephira Crystal. Upon accepting it, Yoshino transformed into a Spirit, an act that miraculously cured her illness. Shortly afterward, she vanished from the hospital and gradually lost all memory of her human life.

Like other Spirits, Yoshino would manifest in the world through Spacequakes, though she occasionally appeared without triggering one. Her powers inadvertently caused rainfall wherever she went, a constant reminder of her sadness and isolation. As a result of the destruction caused by her appearances, she had little to no human contact and was relentlessly pursued by the Anti-Spirit Team (AST). Despite their repeated attempts to kill her, Yoshino refused to retaliate, unwilling to harm others.

Her prolonged isolation and fear led her to create an alter ego, Yoshinon, through ventriloquism with her puppet. Yoshinon embodied the confident, outspoken person Yoshino wished she could be. Over time, Yoshino grew so dependent on this persona that she stopped speaking for herself entirely, allowing Yoshinon to handle all her interactions.

Yoshinon
Yoshinon is Yoshino’s closest companion and personal hero. Originally a gift from her mother, Nagisa Himekawa, the puppet was meant to symbolize Nagisa’s constant presence and protection, even when work prevented her from visiting her daughter. Although Yoshino lost the memory of this origin after forgetting her human life, she remains deeply attached to Yoshinon. To Yoshino, the puppet represents her ideal self, an embodiment of the hero she wishes to be: confident, composed, and never reduced to tears.

Nagisa Himekawa
Nagisa was Yoshino’s mother, a dedicated field worker who single-handedly covered her daughter’s medical expenses. While her demanding job limited her visits, she deeply loved Yoshino and gave her the Yoshinon puppet to ease her loneliness in her absence. Inspired by this gesture, Yoshino began creating a “Yoshinon Junior” puppet to give to her mother as a reciprocal token of care. Tragically, Nagisa died in a workplace accident before Yoshino could deliver the gift.

Shido Itsuka
Shido is Yoshino’s savior and a figure she admires and trusts deeply, seeing him as a hero and protective older brother. She is grateful to him for retrieving Yoshinon and trusts him enough to allow him to seal her powers. While Yoshino’s feelings toward Shido are portrayed as familial, Yoshinon’s teasing remarks occasionally suggest that her affection may extend beyond simple admiration.

Tohka Yatogami
Yoshino first encountered Tohka when the latter interrupted Shido’s initial attempt to make her fall in love with him to seal her Reiryoku. Misunderstandings ensued, during which Yoshinon’s teasing provoked Tohka into snatching the puppet away. The loss distressed Yoshino to the point of summoning her Angel, Zadkiel, in an attempt to retrieve it.

Yoshino’s given name, 四糸乃 (Yoshino), combines 四 (yoshi/shi), meaning “four,” 糸 (ito/shi), meaning “thread,” and 乃 (no), a possessive particle often used in names. While the exact intended meaning is not stated in the series, the inclusion of “four” aligns with the naming pattern of Spirits and their association with Sephirot numbers, with Yoshino’s Sephira being the fourth: Chesed, symbolizing mercy and kindness.

Her family name, 氷芽川 (Himekawa), is composed of 氷 (hyou/koori), meaning “ice,” 芽 (me), meaning “bud” or “sprout,” and 川 (kawa), meaning “river.” The name evokes imagery of a river where ice begins to form or melt, fitting her cryokinetic abilities and gentle personality.

Her Angel, Zadkiel, derives from Hebrew (צדקיאל‎) and means “Righteousness of God,” corresponding to the archangel associated with benevolence and mercy—traits reflected in Yoshino’s compassionate nature.