Leichte is a lone operative for the Black Cross Army, a military faction dedicated to destroying the Iron Army: genetically engineered soldiers designed as living weapons. When her commanding officer vanishes without trace, Leichte has only one lead: a colossal iron tower that serves as the Iron Army's central fortress. She infiltrates this towering stronghold alone, moving through its labyrinthine corridors with nothing but her combat training and determination to find her missing commander, Esus. What begins as a rescue mission quickly becomes something far more complicated. Inside the tower, Leichte encounters corridors that seem designed to disorient, security systems that adapt to her movements, and soldiers who shouldn't be anywhere near this location. The facility holds secrets about the Iron Army's true purpose, the nature of human augmentation, and perhaps even answers about why Esus disappeared in the first place. This is a tense, claustrophobic action narrative that pairs hard sci-fi worldbuilding with intimate character stakes. If you're drawn to military sci-fi with high stakes and mysterious conspiracies, this single-episode ONA delivers concentrated intensity.