This was probably the 100th year since nuclear wastewater entered the sea. During this period, the Neon Country, probably due to some sin, the volcano that had been suppressed for hundreds of years finally erupted, and the island country was almost destroyed. Although this was a joyful thing, when the volcano erupted, it caused a more serious leak of nuclear wastewater. A green rainstorm also swept the world. The end of the world has come, and the surviving humans can only survive in the world after the rain.
Our protagonist, however, encountered a strange mermaid in the dungeon where he grew up, and developed an alternative system.
I don't know if he can end this apocalypse, maybe.
