Tatsumiyajima is the central island in the middle of a small cluster of islands, in a sleepy backwater of the Japanese isles. Not much happens there, and the island's young people go to school knowing that their lives are likely to remain peaceful and undisturbed. Or so they have been taught... but the truth is different. The fate of mankind is on the line, and Tatsumiyajima is the last line of defense against a hostile and incomprehensible enemy. At the center of it all, fighting for Humanity's continued existence, is the giant robot Fafner, the dragon that guards this final treasure of mankind.

[Source: Anime News Network]

Two OVA that summarize the series.

Yumi Ikoma and Ryou Masaoka are children who have been selected to take part in a top secret mission, to be the pilots of the first Fafner combat units; the last chance of survival for the human race. The enemy is ruthless, remorseless and is able to read the minds of humans. Therefore, the details of this mission are kept a secret even from the personnel involved. The young pilots must use all their courage and faith in order to survive and complete their mission or the fate of mankind would be compromised.

[Source: Anime News Network]

Years have passed since Kazuki led a team of young pilots to terminate the alien's home base. Tatsumiya Island is close to recovery, but the scars of war and loss remain with the survivors—and peace remains a distant dream. With Soshi still in its clutches, the enemy uses the humans' own military tactics against them. A mysterious messenger offers an ultimatum for coexistence like a backhanded olive branch: surrender the island's core for assimilation or die. Determined to save his best friend and their only home, Kazuki risks the loss of both body and mind in an explosive battle over the fate of humankind.

[Source: Funimation]

Tatsumiyajima is the central island in the middle of a small cluster of islands, in a sleepy backwater of the Japanese isles. Not much happens there, and the island's young people go to school knowing that their lives are likely to remain peaceful and undisturbed. Or so they have been taught... but the truth is different. The fate of mankind is on the line, and Tatsumiyajima is the last line of defense against a hostile and incomprehensible enemy. At the center of it all, fighting for Humanity's continued existence, is the giant robot Fafner, the dragon that guards this final treasure of mankind. Fafner Exodus will be set 2 years after the first attacks of the festums.

[Source: Crunchyroll]

An expanded version of the first episode of Soukyuu no Fafner: Dead Aggressor - Exodus included in the Blu-ray & DVD Vol.1.

Tatsumiyajima is the central island in the middle of a small cluster of islands, in a sleepy backwater of the Japanese isles. Not much happens there, and the island's young people go to school knowing that their lives are likely to remain peaceful and undisturbed. Or so they have been taught... but the truth is different. The fate of mankind is on the line, and Tatsumiyajima is the last line of defense against a hostile and incomprehensible enemy. At the center of it all, fighting for Humanity's continued existence, is the giant robot Fafner, the dragon that guards this final treasure of mankind. Fafner Exodus will be set 2 years after the first attacks of the festums.

[Source: Crunchyroll]

"Soukyuu no Fafner: The Beyond" episodes 1–3.

"Soukyuu no Fafner: The Beyond" episodes 4–6.

"Soukyuu no Fafner: The Beyond" episodes 7–9.

"Soukyuu no Fafner: The Beyond" episodes 10–12.

Soukyuu no Fafner "peaceful spin-off."