Hinata accidentally discovers the portal to the Byogen Kingdom, left open by Guaiwaru, and tells her friends. Fearing a trap, the girls discuss with their partners the prospect of using the portal to go and fight King Byogen. After a reluctant debate the group decides to go, before the portal closes. In the Byogen Kingdom they encounter King Byogen, who engages Cure Earth before creating Byogen monsters to fight the other Cures. Although the monsters and King Byogen prove too strong at first, their determination allows the Cures to overcome and purify them. Having apparently defeated King Byogen, the girls celebrate, only for their celebration to be interrupted when they are confronted by Guaiwaru, who thanks them for getting rid of King Byogen for him, before revealing the fight isn't over.

Having escaped the Byogen Kingdom, the Cures begin purifying the MegaByogens around Sukoyaka City. With only a GigaByogen left the Cures head to the forest park where the citizens of Sukoyaka have taken refuge to intercept the monster. Meanwhile, Daruizen informs Guaiwaru that the Pretty Cures have escaped and both leave to confront the Cures during the battle with the GigaByogen, where they are also joined by Shindoine, who surprisingly appears to accept Guaiwaru as the new Byogen King. The Byogens manage to overpower the Cures but before Guaiwaru can deal the final blow, Shindoine betrays him and he is absorbed by King Byogen, who thanks to Guaiwaru's power, regains his body. King Byogen reveals that the Cures only destroyed part of his body, and that he was aware of Guaiwaru's treachery, so he planned to use him to regain his power and body with Shindoine's help. King Byogen then powers up the GigaByogen and forces the Cures to fight it. The Cures manage to purify it but find that King Byogen and his generals have disappeared, despite having the advantage. Afterwards, Nodoka and the others return home where they are greeted by their worried parents, who are thankful they are alright. Back in the Byogen Kingdom, King Byogen reveals his plan to use the Cures as bait and attempts to absorb Daruizen into his body, but Daruizen flees to find Nodoka. A wounded Daruizen confronts Nodoka, pleading with her to let him hide in her body to recover but Nodoka runs away terrified.