Jiiro is a primary character from the original anime series. He is an adult male with blue eyes and brown hair that is cut to ear-length. In the world of the story, he is known as a Paladin, a warrior capable of forming a covenant with a Cleric to wield immense power against the giant beasts that threaten humanity. He is initially introduced as a wandering hunter of these beasts, earning a living through this dangerous trade, and is often referred to by the nickname the already dead.

Jiiro's personality is defined by a gruff, cynical, and world-weary demeanor. Having lived through significant trauma and loss, he presents himself as a hardened and battle-scarred individual, often seen indulging in drink and trying to distance himself from the problems of others. Despite this rough exterior, he possesses a deep-seated sense of honor and an inability to look away when an innocent person is in genuine danger. This internal conflict between his desire for isolation and his innate heroic nature is a central aspect of his character.

His primary motivation stems from a profound personal tragedy. In the past, Jiiro was married to a woman named Tohka, who also served as his Cleric and partner. During a battle, Tohka was killed, an event that left Jiiro emotionally shattered and disillusioned with his role as a Paladin. His journey throughout the story is one of reluctant re-engagement with life. Initially seeking only to survive and numb his pain, he is gradually pulled back into a purpose-driven existence when he meets Kuumi, a young and powerful Cleric prototype fleeing from imperial forces. His motivation shifts from simple self-preservation to protecting Kuumi and confronting the dark experiments and political machinations of the empire that created her.

In the story, Jiiro serves as the seasoned protector and reluctant mentor to the protagonist, Kuumi. His role is to be the experienced warrior who provides the skills and combat knowledge necessary for survival, while Kuumi provides the raw, untamed divine power. Together, they perform the Covenant Ritual, merging their abilities to fight giant beasts. He is a key piece in the larger conflict of the world, as his advanced skills as a former elite Paladin make him a valuable asset and a target for the empire's commander and other powerful factions.

Jiiro's key relationships are central to the narrative. His bond with Kuumi is the driving force of the plot, beginning as an inconvenient alliance born of necessity and evolving into a deeper, more trusting partnership built on a shared conviction. This new relationship is constantly contrasted with his painful memories of his late wife, Tohka. His past connection to Tohka also creates a link to other characters, such as Tsurugi and the antagonist Façade, weaving his personal history into the main political and military struggles of the world. His relationship with Myaa, the captain of an airship, also provides practical support for his missions.

Jiiro undergoes significant development from a cynical, isolated drunkard to a man who begins to find purpose again. The protective instinct he feels for Kuumi forces him to confront his past failures and grief rather than run from them. Through these new challenges and bonds, he starts to shed his apathetic shell and re-engage with the world, not just as a survivor, but as a protector once more.

Notable abilities of Jiiro include his exceptional combat skills, which mark him as a cut above ordinary hunters. As a Paladin, his most important ability is the Covenant Ritual, which allows him to become a vessel for a Cleric's godlike power. When he performs this ritual with a Cleric like Kuumi, he can manifest an expandable, weaponized energy spear capable of piercing the hides of enormous giant beasts. His proficiency in this ability, combined with his physical agility and tactical knowledge, makes him a formidable warrior, even in his emotionally drained state.