Warning: Spoilers ahead.
Naofumi’s party have just learned from Kyo that Ost is linked to the core of the Spirit Tortoise. Basically, they must kill her if they hope to kill the Spirit Tortoise.
Then the Spirit Tortoise revives. Its head and heart grow back! Mirelia and Eclair both fear the worst and expect to die in battle with the rest of the armies in the tortoise’s proximity.
The reason the tortoise was able to revive was because Kyo has the three other Cardinal heroes - Itsuki, Motoyasu and Ren - imprisoned, and he’s sucking their power out like a battery for the tortoise!
Asshole Kyo creates a TV screen so Naofumi’s party can see the Tortoise attack outside. The Tortoise fires off its shell missiles at the armies, but the Filolial Queen, Fitoria, appears in the nick of time and protects them with magical barriers. She communicates with Filo, telling them she will aid them by destroying the head from outside. So Naofumi’s party must destroy the heart and core at the same time as her. It’s great to see Fitoria fight because she’s incredibly powerful!
And then more reinforcements arrive. L’arc, Therese and Glass burst through the wall! Kyo tries to convince them to team up, since they all want this world destroyed. But L’arc says their weapons are telling them… not to do something so disgusting. Convenient.
The good guys begin their assault on Kyo. Raphtalia and Filo hit him, but he’s protected by a barrier.
Meanwhile, outside, the Queen orders everyone to retreat so that Fitoria doesn’t have to waste her strength protecting them.
L’arc’s and Naofumi’s parties work together to fight Kyo, but he uses gravity magic to put them all down. He’s able to use the power of the souls the Tortoise gathered to amplify his attacks.
Kyo starts beating up Naofumi, who can’t move. Finally, Rishia goes into super mode and gets up, defying the gravity attack. Her ability with Ki is how she’s able to get up.
She provokes Kyo, calling him a coward with no strength, like herself. He attacks her, but she’s able to dodge easily, and continues to get under his skin.
While Kyo’s busy, Ost grants Naofumi the Spirit Tortoise Shield. He then uses that ultimate spell to free everyone from the gravity effect.
L’arc’s party runs away to destroy the heart. Rishia frees the three Cardinal heroes.
Finally, Naofumi activates his Wrath Shield. But he is unable to use it, because he doesn’t hate Ost. So Ost takes control of his Spirit Tortoise Shield instead, and forces him to destroy the core. Finally the Tortoise dies.
Ost lies on the ground, about to die as well. Bastard Kyo creates a portal to his world and escapes. L’arc’s party follows him into the portal. And with new abilities unlocked, Naofumi’s party follows into the portal after them. Leaving Ost to die alone.