The SSS Commander Left His City to Burn

Reborn a century after the apocalypse, SSS-class commander Eli Cross is betrayed by his ex-girlfriend. Instead of despairing, he binds with Seraphine, a mocked D-class cat spirit hiding legendary power. As they evolve and crush arrogant rivals, Eli exacts brutal revenge. When a monster horde attacks the base that abandoned him, Eli refuses to save them, unleashing Seraphine's ultimate nine-tailed form and walking away.