This is a submarine action story that actually respects the submarine. Not anime submarines with inexplicable physics, but tactics, depth, sonar, the weight of command decisions in a tin can under pressure. Two episodes means no bloat, no filler, no time spent on anything except the next mission and the next threat. If you want naval action stripped down to its core, with hardware that matters as much as the crew, this is built for you.

A year after the unknown organization USR ambushed the founding ceremony of PKN, an alliance of advanced warships meant to keep the oceans at peace, the world's seas remain under threat. USR aims to conquer the world, and its submarine UX, commanded by Admiral Red, is its main weapon. The old submarine 707 once turned the tide at great cost, and its newly built successor, the 707 II, now sets out with former trainees Kenji, Goro and Senta among its crew. When a PKN fleet led by the American battleship Great Guardian falls to USR's assault, the 707 II arrives, and Red eagerly resumes his rivalry with the 707. A two-episode action OVA built around tense underwater battles.