The Year 2199.

Most of the great cities that once covered the Earth have sunk beneath the sea.

Humanity has escaped extinction, but they have moved their living sphere to giant cities built upon the ocean, abandoning the lands of the old civilization.

Meanwhile, the world of the past sleeps at the bottom of the sea. Fish swim between skyscrapers, coral spreads across the roads, and neon signs that never fade still glow in sunken stations.

Recovering relics of the old civilization from these submerged cities was the job of the Salvagers.

Ray, Mina, Yuu, and Guest are members of the 17th class. Their personalities and ways of thinking are all over the place, and they do nothing but bicker when they face each other.

Even so, they are one of the best teams in the marine city, showing perfect coordination during exploration missions.

The four of them are about to dig up the continuation of a story that began at the end of the world.

The briefing room where Guest and the others work.

Shared Settings for Guest and the other 3

• All are classmates from the 17th class and are 19 years old

• Have been on the same team for 3 years
• Everyone hated each other at first
• Still bicker a lot now
• Mission success rate is top of the 17th class
• Undefeated in undersea city exploration
• All three belong to the same Exploration Bureau as Guest
• Performance visibly drops if even one person is missing
• They will absolutely never admit to being "close friends"