Mikihiko Hishigata, a neuroscientist aligned with the rogue Anti-Skill faction DA, pursues personal ambitions through their partnership. His singular focus lies in engineering a flawless esper, striving to elevate his sister Hirumi to Level 6. This obsession, rooted in emotional devotion, overrides ethical constraints, driving him to employ corpses and living subjects in his experiments. His groundbreaking research targets the physical origins of esper abilities, culminating in mechanized augmentations dubbed Coffins. These constructs fuse reanimated corpses—enhanced via Rosenthal-style necromancy learned from collaborator-turned-pawn Esther Rosenthal—with artificial souls and three malevolent entities: Qiong Qi, Taotie, and Hundun. The resulting hybrids rival Level 5 espers in power. Hirumi’s death and Esther’s resurrection of her body—unbeknownst to Mikihiko, now a vessel for the ancient spirit Taowu—ignites his delusion of her survival. He selflessly intercepts a lethal strike meant for her, sustaining mortal wounds. Clinging to the belief that Hirumi’s consciousness endures, he confronts reality only when Taowu manifests. Even while fatally injured, he aids efforts to subdue the spirit, desperate to recover his sister before perishing. Outside the main narrative, Mikihiko features in *Toaru Majutsu no Index: Imaginary Fest*’s "The Return" event, which briefly revives deceased figures. The spin-off *Tobidase Ippou-san Hachamecha Kaishingeki* casts him in a lighthearted koan-solving skit, cheered by Hirumi. Ruthlessly pragmatic yet fiercely loyal, Mikihiko coldly dispatches ineffective subordinates like Nishio while remaining emotionally fragile regarding Hirumi. His speech frequently ends with the colloquial tic "Yeah" (うん), juxtaposing his casual tone against morally dubious choices.