Jun Nori had never known a world without water. He was born on Aqua, the new home of humanity, and had grown up on one of the floating islands that dotted the ocean surface. The island was a small community, with only a few hundred people, but it was a close-knit group, and Jun knew everyone by name.

Jun had always been fascinated by the legends of the Cloud Riders, the elite pilots who could fly through the clouds that hung high above Aqua. The Cloud Riders were said to have technology that could restore Earth's atmosphere, making it habitable once again for humans. Jun dreamed of one day joining their ranks and helping to rebuild the lost world.

As a child, Jun would often spend hours watching the clouds, imagining himself soaring through them on a sleek flying machine. He would make models of aircraft out of found objects and pretend to pilot them through the air. His parents indulged his imagination, encouraging him to pursue his dreams.

When Jun turned eighteen, he decided it was time to make his dream a reality. He applied to the Cloud Rider Academy, a prestigious institution that trained the best pilots on Aqua. The application process was rigorous, with extensive tests of both physical and mental aptitude, but Jun was determined to succeed.

Finally, after months of waiting, Jun received his acceptance letter. He was overjoyed and couldn't wait to begin his training. He said goodbye to his parents and friends and set off to the academy, located on a larger island that housed hundreds of students.

The first day of training was grueling, with hours of physical exercise, classroom instruction, and simulator time. Jun found it all challenging, but he was determined to succeed. He made friends with his fellow cadets, including Maya, an engineering prodigy, and Kato, a fearless pilot.

As the weeks went by, Jun's skills improved. He learned how to control the winds and currents, navigate through stormy weather, and operate advanced flying machines. He also learned about the history of the Cloud Riders and their mission to restore Earth's atmosphere.

One day, during a break in training, Jun and his friends were walking along the beach when they saw something unusual in the sky. It was a cloud, but it was unlike any they had ever seen before. It was glowing with a strange light and seemed to be pulsing.

"What is that?" Maya asked.

"I don't know," Kato replied. "But we should report it to the academy."

Jun nodded in agreement, and the three of them hurried back to the academy to inform their instructors. When they arrived, they were met with a flurry of activity. The Cloud Riders had detected the strange cloud too and were preparing to investigate.

Jun and his friends were eager to join the mission, but they were told that they were not yet ready. They would have to continue their training and prove themselves before they could be allowed to fly into the unknown.

But Jun couldn't stop thinking about the strange cloud. What could it be? And what did it mean for the future of humanity on Aqua? He knew that he had to find out.