In a future where sentient warships called "Fleet of Fog" have mysteriously appeared and blockaded humanity's oceans, the Japanese Navy discovers an unprecedented ally: Iona, a submarine from the enemy fleet who chooses to fight alongside mankind. Together with her human captain and a crew of unconventional naval officers, Iona must navigate the impossible terrain between two worlds, protecting humanity from the very force she once served while grappling with questions of identity and loyalty that threaten to tear her apart. This film compiles the most pivotal moments from the original series while introducing new sequences that deepen the mystery surrounding the Fog's origins and Iona's defection. Expect intense naval combat sequences rendered with meticulous mechanical detail, philosophical tension between duty and choice, and a protagonist caught between steel and soul. The atmosphere balances high-octane action with quiet introspection, creating space for genuine character development amid the spectacle. Viewers drawn to science fiction stories about unlikely alliances, artificial consciousness, and warfare will find themselves invested in Iona's struggle to forge her own path.