Mysterious monsters appear as Naofumi is preparing for the next Wave. At the same time they show up, the Wave countdown stops. The Queen summons the Four Cardinal Heroes, and tells them that the Spirit Tortoise has revived.

The leaders of all the nations’ militaries gather in the Spirit Tortoise Kingdom. Naofumi is there as well, and promises to offer his help as one of the heroes. But just before they decide on a plan, a mysterious woman appears…

The Spirit Tortoise begins its march once more, appearing at the border of the kingdom bearing its name. Naofumi volunteers to lure away its familiars while the army tries to bring it to the mountains. The Spirit Tortoise’s familiar, Ost, fights alongside the humans…

The Spirit Tortoise’s head was cut off, but Ost, its familiar, is still alive. It could revive at any moment. The allied armies need to get back into fighting shape, and fast. Naofumi makes the risky move of heading onto the Tortoise’s back with only a small group, and tries to find its true weak spot.

Fitoria appears when the Spirit Tortoise revives, and with her help, Naofumi attempts to destroy its heart and cut off its head at the same time. L’Arc arrives as well, but all of them are helpless before Kyo’s overwhelming power.

Naofumi wakes up in a strange prison to find him and his party at level 1, and Filo missing. They start to raise their levels in order to escape, but things quickly turn against them when a dangerous monster suddenly appears…

The Wave appears before its scheduled time. Kizuna's group is teleported to it while Naofumi and his party head for Kyo's lab on Ethnobalt's ship. There, they see the true depths of Kyo's wickedness...

Raphtalia recalls having to buy clothing for her smaller self. Kizuna remembers being alone for so long. Rishia remembers Ost trying to give advice.