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.

To the Cures' horror, Neo King Byogen uses his power to infect all of Sukoyaka City at once with the resulting infection also gradually spreading worldwide. Determined to restore the city by purifying the king, the Cures attempt to engage Neo King Byogen but discover he is protected by a barrier; he also effortlessly defeats them, causing them to lose their transformations. However, Queen Teatine arrives in time to help the Cures; using her powers along with her Healing Animal friends, she creates a barrier to contain Neo King Byogen and stop his infection temporarily, allowing the girls time to figure out how to defeat him. However, they are forced to flee when Shindoine attacks them, with Asumi using her wind powers to transport them outside Teatine's barrier. During their moment of respite, Asumi reveals she may have a way to counter Neo King Byogen's barrier: by using the Byogens' power along with their own, they should be able to pass through it. However in order to do so, Asumi must take in a Mega Part so she can use Byogen power. Despite initial protests, everyone agrees after seeing Asumi's resolve. Shindoine appears once again and the girls transform to fight her, hoping to get her remaining Mega Part, however Shindoine uses it to become stronger. After an arduous battle, the Cures manage to defeat Shindoine using Final Healin' Good Shower, restoring her to her original form, but Rate manages to tell them to use Healing Oasis to purify Shindoine further and allow Cure Earth to absorb her Byogen particle. Now with the ability to combat Neo King Byogen, the Cures prepare to face him.