Shin, the younger twin brother of Shun, grows up under the care of villagers following their parents’ demise. Trained since childhood to combat monsters and defend their home, he adopts a brash, self-centered exterior, masking deep-seated grief over Shun’s death with indifference and suspicion toward strangers. When tasked with securing the clavis crystal after his brother’s passing, Shin clashes with Asuna, who initially confuses him for Shun. His abrasive hostility slowly erodes through their shared trials, revealing reluctant acts of loyalty—such as shielding her from the Izoku, despite injuries that jeopardize his mission. As tensions escalate in Agartha, Shin’s rigid obedience to duty fractures. He defies village mandates to ally with Asuna and Morisaki, culminating in his destruction of the clavis crystal to liberate Asuna from possession, a defiance that severs Morisaki’s leverage. This choice, rejecting cold pragmatism for empathy, mirrors his unraveling emotional walls: he tearfully confesses his identity to Asuna, exposing unresolved anguish over Shun’s absence. By the journey’s end, Shin urges Morisaki to embrace life amid despair, embodying his own hard-won resolve to honor loss without being consumed by it. He remains in Agartha, having aided Asuna’s return home—a figure tempered by sacrifice, carrying his brother’s memory while forging fragile hope in human connection.