Thirty years prior to the main events, Shinji Takamiya (崇宮 真士, Takamiya Shinji) encountered the First Spirit during a catastrophic Spacequake. Bringing her to his home, where he lived with his younger sister Mana, Shinji offered her shelter. After brief media attention, the Spirit learned to speak and revealed what she understood about her origins. Wishing to integrate her into his life, Shinji named her Mio Takamiya, inspired by the date they met the 30th of the month. Over time, the two developed romantic feelings, with Shinji winning Mio a cherished teddy bear from a crane game and later taking her on a beach outing.

Their peace was shattered when DEM Industries discovered Mio’s location. Assisted by Elliot Baldwin Woodman, Shinji attempted to protect her from Isaac Ray Pelham Westcott, who claimed to have captured Mana and offered to exchange her for Mio. Refusing to trust Westcott, Shinji tried to flee but was fatally shot. Stricken by grief and unable to revive him directly, Mio absorbed Shinji’s body into her own, intending to reconstruct him and grant him her powers so he could remain with her forever. However, the human body could not withstand the full extent of Spirit abilities, so she bestowed upon the reborn Shido only a single gift, the capacity to gradually seal the powers of other Spirits within himself.

After his rebirth, Shido was abandoned by Mio and adopted into the Itsuka household. Though he had no clear memories of his “mother,” her absence plunged him into a year-long period of deep depression. Five years prior to the present, an incident caused his foster sister Kotori Itsuka to become a Spirit due to manipulation and misunderstanding. Neither Kotori nor Shido retained memories of the event until Kotori later reactivated her powers, triggering their recollection. Around the same time, the organization Ratatoskr discovered Shido’s unique sealing ability.

Before this incident, Shido had a brief connection with Origami Tobiichi, who lived in the same district. She claimed to have met him years earlier, though Shido had no memory of it. It was later revealed during the events of Tobiichi Devil that Origami had actually encountered a future version of Shido, who had traveled back five years using Kurumi Tokisaki’sand altered his physical form with Natsumi’s power. In the past, he rescued the 11-year-old Origami from debris during a fire and offered her words of comfort, urging her to entrust her emotions to him everything except her anger toward the Spirit responsible for her parents’ deaths.

Shido has the looks of a handsome young man in high school. He has straight blue hair and bands down to his neck and amber-brown eyes. During the times when he borrows another Spirit’s power, the color of his eyes turns into a more golden shade. He is often seen wearing the male Raizen High School uniform during his everyday life circumstances.

During the events of Miku Lily, Shido had to cross-dress as a girl to interact with Miku, thereby disguising himself as his alternate identity, Shiori Itsuka (五河いつか 士織しおり?). During that time, he was seen with long blue hair, and he wore the standard female Raizen High School uniform. He also wore a flower hair clip as a hair accessory. He is later able to become physically female via Haniel.

Shido is portrayed as an ordinary high school student who initially had little interest in romance, particularly toward the opposite sex, until his adoptive sister Kotori pressured him into interacting with girls more frequently. This sudden change in his social life forced him into situations he had little experience handling.

Kotori has noted that Shido’s compassion stems largely from his abandonment by his birth mother, which left him unusually sensitive to the despair of others. This empathy makes him particularly suited to dealing with Spirits, who often suffer from emotional isolation. His genuine kindness and willingness to understand others have been key factors in earning the trust and affection of many Spirits. Even those initially hostile, such as Miku Izayoi, were ultimately swayed by his ability to see and accept them as individuals.

Shido is characterized by a strong will, an enduring sense of forgiveness, and a readiness to risk himself for others. He consistently pursues the goal of saving Spirits regardless of the danger, often downplaying the harm they have caused him. For example, after Natsumi nearly destroyed his reputation and erased his existence, Shido dismissed her actions as nothing more than “childish pranks.”

In middle school, Shido went through a chuunibyou phase, during which he played guitar, wrote stories and poems, and invented dramatic “special moves” inspired by anime. He now finds this past embarrassing and tries to erase evidence of it, though Kotori has kept these mementos as leverage during his training.

Under the influence of a heightened Reiryoku state, Shido’s personality becomes more confident, flirtatious, and uninhibited. In this form, he openly attempts to charm nearly every girl he meets, including his enemies, and is unfazed by close physical contact. He even uses his sealed Spirit powers for amusement. However, if his Reiryoku spirals out of control, he loses his rationality and becomes a destructive, mindless entity, regaining his senses only through the Spirits reopening their emotional bonds with him via a kiss.

Despite his determination, Shido’s resolve can waver when confronted with harsh truths. Upon learning the full extent of Kurumi Tokisaki’s violent nature, he became fearful and hesitant to face her. Similarly, when Mukuro Hoshimiya rejected him and accused him of hypocrisy, he began to question whether sealing Spirits’ powers was the right course of action, as it left them more vulnerable to capture by DEM Industries. In such moments, Shido relies on the counsel and support of his allies to reaffirm his beliefs.

Tatsuo Itsuka and Haruko Itsuka
Tatsuo and Haruko are Shido’s adoptive parents, to whom he feels deeply indebted for taking him in as a child. Out of gratitude, Shido often dotes on their daughter, Kotori, and takes his responsibilities as her older brother seriously. His parents trust him enough to leave him in charge of both Kotori and their home while they are overseas.

In his past life as Shinji Takamiya, Tatsuo had been his classmate and close friend. After regaining the memories of this previous existence from Mio Takamiya, Shido and his adoptive parents became aware of their past connection, though this knowledge did not significantly alter their current relationship.

Kotori Itsuka
Shido and Kotori share a close sibling bond despite not being related by blood. They have lived together for many years, with Shido showing a deep protective instinct toward her. During a Spacequake alert, he once rushed out in concern for Kotori, believing she was at a family restaurant due to an earlier promise. Five years before the present events, he gave her a pair of black ribbons for her birthday, telling her that wearing them would allow her to become her “strong self,” as a way to help her overcome her tendency to cry easily.

Mana Takamiya
Mana is Shido’s biological younger sister, though they were separated for many years. Upon reuniting, Mana greeted him with a hug and called him “big brother,” surprising Shido. Both admitted to having no memory of one another, but Mana carried a pendant with a childhood photograph of the two together. While initially shocked, Shido quickly accepted her presence in his life and welcomed the newfound sibling relationship.

Mio Takamiya
Shido was created by Mio as part of her plan to resurrect Shinji Takamiya, making her his mother in a technical sense. However, Mio viewed him solely as Shinji’s reincarnation and failed to acknowledge him as an individual. Although Shido understood her grief, he was disturbed by the extent of her sacrifices in pursuit of this goal. His unease grew when Mio revealed her intention to erase his memories as Shido so that her envisioned Shinji would not feel guilt over her actions. In the Game Over timeline, their opposing ideals led them to become enemies, forcing Shido to use Kurumi Tokisaki’sto travel back in time and prevent the widespread loss of life caused by Mio.

Shido’s given name, 士道 (Shidō), is composed of the kanji 士 (shi), meaning “warrior” or “gentleman,” and 道 (dō), meaning “way” or “path.” Together, the name can be interpreted as “the way of the warrior” or “path of the gentleman,” reflecting his role as someone who protects and guides the Spirits.

His family name, 五河 (Itsuka), combines 五 (itsu/go), meaning “five,” and 河 (kawa/ka), meaning “river.” While the meaning is not explicitly referenced in the series, it could be read metaphorically as “five rivers,” possibly symbolizing multiple paths or connections converging into one, a fitting theme for a character whose life intertwines with numerous Spirits.

Shido’s female alias, 士織 (Shiori), retains the first kanji from his given name, 士 (“warrior” or “gentleman”), while replacing 道 with 織 (ori/shoku), meaning “weave” or “fabric.” This could symbolize the weaving together of relationships or events, tying into his role in connecting with Spirits to seal their powers.