Athena Saori watches over peace on Earth from Sanctuary and over young Kōga, until an invader causes commotion when he tries to kidnap Athena and the baby. Kōga is saved from certain death by the timely arrival of Gold Saint Seiya, who engages the mysterious invader, who reveals his identity as Mars. A new conflict begins as Seiya and Mars battle for the fate of Kōga, who years later, determined to live his life as he sees fit, challenges Athena.

Eden sees his own darkness as Aria is constantly being used by Mars without the power to do anything about it, before being confronted by his parents about his destiny for the new world. Accepting whatever punishment that would be suitable for his errors, Eden allows himself to succumb to his darkness. Meanwhile, tormented by her own darkness of being used as an instrument of destruction Aria resolves to use her Light to protect those who need her, in doing so she reaches both Eden and Kouga from their darkness and all reach the Core of Darkness. Aria then along Kouga...

Abzu tries to have Kouga under his control once more with no success and his attempts to kill Saori are stopped by his desperate efforts. Once feeling the radiance of his Cosmo, Kouga's friends send the last of their energies to assist him. Infused with the power of his companions and protected by Aria's light, Kouga manages to rescue Saori and destroy Abzu for good. As Earth regains the Cosmo that was siphoned from it, the planet returns to normal and the corruption that has spread into the Saints' bodies is washed away. After a brief encounter with Aria's spirit, ...

Once the saints infiltrate the city, Seiya draws the attention of the enemy allowing Koga and the others to push forward. However, Tarvos appears to challenge Koga to a decisive battle and Ryuhou stays behind to assist him.

To increase his power for his rematch against Yuna and Souma, Methone uses a dreadful item given to him by Europa to kill his sister Ymir and drain her Cosmo, and the two Bronze Saints must combine their strengths against the empowered Pallasite, as they reminisce upon the day they first met.

As Koga and his friends approach Pallas' fortress, Mira appears before them again, but Ikki arrives in the nick of time to protect them. After the Pallasite flees, Ikki reveals to the other Bronze Saints that Pallas is not their greatest enemy, but an even greater foe who is manipulating the whole conflict from the shadows.