Issei was lucky to be alive, barely. Emerald was a skilled Corporeal Agno who did all he could to stabilize him after the encounter with Himawari's Golden Archer technique. She had fired the last projectile through his Tyo'men which completely destroyed it along with his left eye. Thanks to this swift response to his injuries, Issei's brain only suffered minor injuries despite costing him quite a bit in the sense that he could no mould kaimei. All he could do was create and oust it from his body. The only way he could have resisted was by releasing repulsive kaimatic shockwaves to keep his interrogators at bay — not that the K.O.S. Military would permit it.