Saeko

was the wife of the Kawaguchi Metal Fittings Corporation's manager. She was infected by the Human Body Ignition Phenomenon, turning her into a Flame Human.

Appearance
As a Flame Human, Saeko had fiery flowing hair, and black charcoal-like skin with the rest of her body being enveloped in flames, no mouth and solid-colored eyes with black sclera.

Personality
While a Flame Human, Saeko was peculiarly intelligent. As usual to Flame Humans, she was driven by rampage and chaos, and burned everything in sight. She was protective of the Kawaguchi Metal Fittings Corporation, quite possibly due to her husband's affiliation with the factory. In battle, she was very cautious of her surroundings.

Introduction arc
Saeko turns into a Flame Human and begins rampaging in her husband's workplace, forcing the 8th Special Fire Brigade to arrive at the scene. Sneaking up behind Shinra, she absorbs the flames around her and strikes the boy, blowing him away and leaving him unconscious. As Shinra regains awareness, Saeko rushes towards the brigade, noticeably more adept in battle and quick on her feet compared to the other Flame Human that Shinra witnessed at the train station. She is stopped by Akitaru, with Maki blasting away the flames to prevent her team-mate from getting burned. The man then uses his weapon attack, aiming to impale the being's core, but Saeko counterattacks and hits the weapon out of his hands, forcing the brigade to separate to safety. As Shinra recalls his past and promise to his mother, the boy charges towards Saeko with a blazing kick, successfully impaling her core and sending the woman's soul off into the "raging flames". When the brigade leaves the factory, Saeko's husband, who was waiting outside, bursts into tears while thanking Shinra that they were able to send her off peacefully.