After Dr. Kuro was captured, Black Sun's forces suffered heavy losses. The City Hall sent an email announcing the lifting of Kosu and Jinpei's ban on entering dungeons. Kosu and Jinpei were relieved that they could finally go back to the dungeon. The virtual training in the Dungeon of Earth had been helpful, but they were itching to test their new skills in the real world.

They received a new request from the city hall, this time to investigate a dungeon that was causing some trouble in a nearby town. They accepted the mission and made their way to the town.

Upon arrival, they could see that the town was in a state of chaos. The dungeon had spawned all sorts of monsters, and the town's people were struggling to keep them at bay. Kosu and Jinpei knew that they had to act quickly.

They made their way to the entrance of the dungeon and descended into its depths. The monsters they encountered were stronger than the ones they had faced before, but Kosu and Jinpei's training paid off, and they managed to defeat them one by one.

As they went deeper into the dungeon, they noticed that the architecture was different from the dungeons they had been to before. The walls were made of strange materials, and there were strange runes etched into them.

Jinpei recognized the runes as belonging to an ancient civilization that had long been lost to history. He couldn't believe that they had stumbled upon a dungeon that was connected to this civilization.

They finally reached the deepest part of the dungeon, and there they found an artifact that was emitting a strange energy. They realized that this was what was causing the monsters to spawn.

Suddenly, they heard a voice behind them. It was a man in a black suit, who introduced himself as a member of a secret organization that had been using the dungeon as a testing ground for their experiments.

He revealed that they were trying to harness the power of the ancient civilization to create a weapon of mass destruction. Kosu and Jinpei knew that they had to stop them.

The man in the black suit pulled out a strange device and aimed it at Kosu and Jinpei. He activated it, and a powerful energy blast was unleashed.

Kosu and Jinpei dodged the blast, and Kosu remembered his new technique. He launched his Mind Slash from a distance and struck the man in the black suit, causing him to drop the device.

They quickly defeated the man and destroyed the device, neutralizing the artifact's energy.

Kosu and Jinpei reported everything they had found to the city hall and were praised for their bravery. They couldn't wait to see what other mysteries lay hidden in the depths of the dungeons they would explore next.