By 2039, humanity confronts a crisis as sea levels surge to unprecedented heights. The rising waters threaten coastal cities, forcing governments to scramble for solutions. Compounding the peril, formidable foes in the shape of ancient warships—known as the Fleet of Fog—patrol the seas, cloaked in mist and equipped with stealth tech. These vessels cut off communication and trade routes across multiple regions, leaving isolated populations in peril.
All conventional countermeasures fail against these adversaries. Only Gunzou Chihaya, helming the allied submarine Iona (Fog I‑401), holds any realistic chance. Consequently, Japanese authorities assign Gunzou and his crew, dubbed Blue Steel, a vital mission: they must transport the final weapon of hope—the Vibration Torpedo Warhead—through hostile waters, navigating minefields, evading patrols, to Washington for large‑scale production.
Despite their involvement in this grim conflict, Blue Steel seeks merely a peaceful end. Their oath is to protect humanity without resorting to unnecessary violence, and they remain steadfastly committed to that principle even amid severe adversity. As Iona carries out the assignment and duties, the crew upholds their values with unwavering resolve.
Sanzigen Japan