In the near future, in response to a series of attacks on ships and ports by an organization known as the USR (Undersea/Underwater Silence Revolution), the nations of the world have formed the PKN (Peace Keeping Navy). At the inaugural meeting, the USR commander Admiral Red launches an attack with his advanced submarine, the U-X. When the flagship is in danger of being sunk, the Japanese contribution to the navy, the 707, which arrived late, steers into the path of the torpedoes and is sunk. The 707 is salvaged and rebuilt, and six months later, it's crew set out to sea to fight Admiral Red.
- Big Bad: Admiral Red.
- Curb-Stomp Battle: What the U-X usually delivers, except against the 707R.
- Flaunting Your Fleets: The PKN does this at the start, giving Admiral Red a chance to attack them.
- Hot Sub-on-Sub Action
- Macross Missile Massacre: The U-X sinks two ships with these in the beginning of the OVA.