Born as Sha Jien, Dokugakuji is the older half-brother of Sha Gojyo, one of the main protagonists. Unlike Gojyo, who is half-human, Dokugakuji is a full youkai, being the son of his father's legal wife. Their family was fractured when their father took a human mistress, resulting in Gojyo's birth. After the deaths of their father and his mistress, Gojyo came to live with Dokugakuji and his mother. While the bond between the two brothers was strong, Dokugakuji's mother was driven mad by her husband's infidelity and took out her frustrations on Gojyo. In an attempt to placate her and assume his dead father's role, Dokugakuji even resorted to having a sexual relationship with his own mother. This tragic situation culminated in a violent confrontation where the mother, intending to kill Gojyo, scratched his face, leaving him with permanent scars. As she cornered the young Gojyo, who had resigned himself to death, Dokugakuji intervened and killed her to save his brother. Overcome with guilt and unable to cope with what he had done, Dokugakuji abandoned Gojyo soon after. Roughly six years before the main story begins, a wandering Dokugakuji was taken in by the youkai prince Kougaiji at Houtou Castle. In service to the prince, he abandoned his former name and took the name Dokugakuji.

Dokugakuji embodies the archetypal older brother, displaying a protective and watchful nature over those he considers his charges. Despite his traumatic past, his outward demeanor is often laid-back and easygoing, and he is known to address his lord Kougaiji by the casual nickname Kou. He possesses a strong sense of honor and loyalty, which he holds in high regard. However, beneath this calm and confident exterior lies a deep well of self-hatred and guilt. He has never forgiven himself for failing to protect his younger brother Gojyo in their youth and for the act of killing his own mother. This past trauma drives his primary motivation: to be a perfect protector for his new lord, Kougaiji, seeing in him a surrogate for the brother he feels he failed. His dedication is absolute, having pledged his very being to Kougaiji who took him in without question when he had nothing.

In the story, Dokugakuji serves as a recurring antagonist and a rival to the Sanzo party, primarily acting as the bodyguard and the muscle for Kougaiji's group. He is a formidable warrior whose path frequently crosses with the protagonists as both groups search for scriptures or confront the machinations of Gyokumen Koushu. His role is not purely villainous, as the conflicts are often driven by circumstance and opposing loyalties rather than pure malice. His most significant relationships are with his lord and his blood relative. His relationship with Kougaiji is the most central to his identity. He projects his feelings of brotherly love and his need for atonement onto the prince, striving to protect him from any harm, a mission that becomes deeply personal after events where Kougaiji is injured and brainwashed by the scientist Dr. Ni. Dokugakuji blames himself for this failure, feeling he has been selfish in forcing his own trauma-driven need to protect onto Kougaiji. With Yaone, a fellow loyal servant of Kougaiji, he shares a supportive and understanding bond; they work together seamlessly and provide each other with emotional strength during times of crisis for their lord and his sister Lirin. His relationship with his half-brother Sha Gojyo is one of the most poignant. Now on opposing sides, they frequently meet as enemies on the battlefield, often fighting each other directly. Despite this, a clear undercurrent of affection and fond memories remains between them; their brotherly love does not vanish even as they clash with witty banter, each having chosen their own path in life.

Dokugakuji undergoes notable development as he is forced to confront his past failures. His deep-seated guilt over killing his mother and abandoning Gojyo is the lens through which he views his duty to Kougaiji. When he fails to protect Kougaiji from Dr. Ni's machinations, it forces him to re-evaluate his motivations with the help of Yaone. He acknowledges his selfishness in using Kougaiji as a substitute for Gojyo, but resolves to strengthen his resolve to save his lord on his own terms, thus transforming his guilt into a more mature and selfless form of loyalty. As a warrior, Dokugakuji is a highly skilled combatant. His primary weapon is a large, summoned curved sword with an eye set into the hilt. He can summon this sword in a manner similar to the way other characters summon their signature weapons. His fighting style is direct and powerful, making him a physically formidable opponent who usually matches up against his brother Gojyo when their groups clash.