sla, a flying island, is about to leave for the "end of the sky". At the sailing ceremony, there was Karuel, an apprentice as an aviator. Contrary to the atmosphere of the gorgeous ceremony, Karuel's eyes, which fly the air plane, were hated by Provincial Superior Nina Viento of Isla.

Karuel is worried about Claire who happened to meet on the shore of the lake. Karuel, who enrolled in the flight department of Kadokesu High School and became a centejual group, will form a flight pair in practical training and apply for a pair to Claire. However, Faust of the Vanville group has a connection ...

Karuel invites Claire to the Kadokez dormitory. Ariel treats you with exquisite curry, Claire's tension is relaxed, and you can naturally relax with the dormitory students. It's been a month since Karuel and his friends entered the school, and the flight exercises will be air combat specifications such as sniping with rifles and flying in formation .

Caruel was in distress with Claire due to Faust's scheme. El Archon is landed in the sea and waits for rescue, but it rains and thunder begins to thunder .... Meanwhile, Ariel, worried about the Caruels, remembered the day when his father Michael brought a young Caruel home.

Four months have passed since the departure, and Isla has come close to the Holy Spring. The flying students decided to camp on the shore of the lake after conducting rigorous ground warfare training under the blue sky in midsummer. It was a fun and peaceful camp, but Claire's expression was dark and she tried to keep a distance from Karuel for some reason.

Isla arrives at the Holy Spring, which is expected to be the center of the world. Flying students are impressed by the magnificent scenery. The city celebrates the arrival of the Holy Spring and is in a festive mood. However, the other day, it was confirmed that the Knights shot down and captured the "Clan of the Sky" with aerial power, and dark clouds rushed into the future journey.

Knights were among the first to discover a fleet of empty clans that "unconditionally attack anything that enters the Holy Spring ." The old-fashioned wooden destroyer fleet is scary, and Leopold is annihilated with all his might. Around that time, Chiharu and Mitsuo, who were scouting the rear airspace, discovered an enemy super-large bomber ...

whose main force has been torn off, is bombed by the strategy of the Sky Clan. Karuel and his friends, who had been on standby in Isla, take off at El Archon at their own discretion to protect Isla . However, he was shot down one after another by the formation of the enemy mantis, and was driven into inferiority.

Two days after being bombed by an air clan, a joint funeral was held, and Chiharu , who lost Mitsuo , burst into tears. That night, Karuel and Claire, suffering from the death of a classmate, happen to meet again in front of the tombstone. Karuel hugs Claire and expresses her feelings, but Claire says something unexpected.

Karuel wakes up when she hears from Ignacio that Ariel gives up the aviator because of an injury and Claire who reveals her identity leaves school because of herself. At that time, an alarm sounds in the sky of Isla. A sortie order was also issued to the flying air student, but it was to become a decoy of the observation aircraft ....

Noriaki and Benjamin decide to take over the observation aircraft on behalf of the one that was shot down. Karuel and Ignacio protect the two, attracting enemy planes and becoming decoys. Beyond Karuel's line of sight, Claire stands on the deck of Luna Barco , who is about to sink.

The request of the Sky Clan to negotiate a truce with Isla was the character of the wind-calling girl Nina Viento. Karuel, who had the opportunity to intervene with Ignacio, hits her on the day of departure. Isla, who continued to sail, finally arrives at the destination of the trip, "the end of the sky."

After arbitrating with the Sky Clan and finding the "End of the Sky," Isla finishes her role and the inhabitants return to the Republic of Ballesteros. In front of the people who filled the venue for the triumphal ceremony, Karuel reveals that he is the first prince of the former Ballesteros Empire, Karl La Hire, and expresses his feelings.