Iska is the sixteen-year-old protagonist of the story, a boy soldier belonging to the scientifically advanced Empire. His background is defined by a meteoric rise and a dramatic fall, as he became the youngest person ever to achieve the rank of Saint Disciple, the Empire's highest military honor. However, this status was stripped from him after he committed an act of treason: he facilitated the escape of a captured witch, an act of mercy that led to a lifetime prison sentence. Despite this, the ongoing war against the Nebulis Sovereignty, the so-called Land of Witches, leads to his conditional release. He is given a chance to earn his freedom by accomplishing a near-impossible task: capturing the Sovereignty's most formidable warrior, the Ice Calamity Witch, Aliceliese Lou Nebulis IX.

On the surface, Iska presents a calm and peaceful demeanor. He has a genuine appreciation for the arts, including theater, classical music, and painting, and enjoys simple pleasures like Italian food, particularly pasta. This gentle exterior, however, masks an incredibly stubborn and fiercely determined core. His approach to combat is the source of his ironic nickname, the peace-loving war nut, as he is a relentless fighter who despises conflict. He possesses a strong, unshakeable moral code, refusing to view all witches as mere monsters and showing kindness and restraint even to his enemies, often choosing to incapacitate rather than kill. This idealism can sometimes lead to rash, short-sighted decisions, a flaw that directly led to his imprisonment and is noted by his more pragmatic comrades.

Iska’s primary motivation is to end the centuries-long, seemingly pointless war between the Empire and the Nebulis Sovereignty. His plan to achieve this peace is radical and direct: to capture a high-ranking purebred witch, using them as a hostage to force a truce. This singular goal fuels his every action and makes him immune to offers of power or alliance from either side. In the story, this mission places him in direct conflict with his arch-rival, Aliceliese, but also fatefully reunites him with the witch he freed, Sisbell Lou Nebulis IX, who is Aliceliese's younger sister. This connection entangles him in the political intrigues and power struggles of the Sovereignty's royal family.

His role in the narrative is defined by these paradoxical relationships. He is a loyal soldier of the Empire who repeatedly defies its orders and prejudices to protect his enemies. His most significant relationship is with Aliceliese. They begin as mortal enemies on the battlefield, but through a series of chance encounters in neutral territories, they discover a deep, unspoken kinship. Their tastes in food and art are eerily similar, and they find themselves forced into reluctant, temporary alliances against common threats. This dynamic gradually evolves from pure rivalry into an unacknowledged romantic attraction, though both prioritize their duties to their respective nations over personal feelings. Iska also becomes a figure of fascination for the other princesses, with Sisbell developing a deep admiration for him and even the first princess, Elletear, taking an interest in him, making him an unexpected focal point for the Sovereignty’s internal affairs.

Throughout his development, Iska is forced to confront the flaws within his own nation. His journey from a celebrated Saint Disciple to a convicted traitor and then to a reluctant operative reveals the Empire’s darker secrets and its own brand of cruelty, challenging his initial worldview. Despite the pressure and complexity, he does not waver from his core goal of achieving peace, though the means by which he hopes to achieve it are constantly tested.

Iska’s notable abilities are deeply tied to his unique weapon, the Astral Swords. He is the sole wielder of this pair of black and white twin swords, earning him the title Successor of Black Steel. The black sword possesses the power to completely nullify any star spirit magic it cuts. The white sword can then replicate and use that same nullified magic a single time. This rare power makes him the ultimate anti-mage warrior, leading his mentor to claim he will never lose to a magic user. However, this specialization comes at a cost; against purely physical opponents, his swordsmanship is merely average. His true strength lies not in natural talent but in relentless training and an indomitable will that allows him to stand against far more powerful foes.