Submarine 707R

The PKN organization was established to maintain ocean peace through a coalition of advanced warships from various countries. However, during its founding ceremony, the organization was ambushed by the unidentified group USR, which aimed to conquer the world. The USR submarine UX operated by Admiral Red was initially thwarted by the old Japanese submarine 707, commanded by Captain Hayami, but at great personal risk. A year later, the 707 II, a replacement for the damaged 707, set sail with a new crew, including trainees Kenji, Goro, and Senta.