The movie initiates with its main antagonist, the Dark Witch, revealing the view of her crystal ball and preparing to steal the Garden of Hope's Diamond Line. As one of the servants of the Dotsuku Zone, she orders a bat-formed Zakenna to prepare the ship.
Meanwhile, Nagisa and Honoka are eating at Tako Cafe, and Akane says that if Nagisa keeps eating so fast and improperly, she'll never find a boyfriend. Nagisa proves that she'll find someone who will love her just like she is. Hikari asked if she meant Fujimura Shougo from high school, while Nagisa got all blushed and kept denying. Then he accidentally came near with Kimata. Nagisa's face shifted red and had takoyaki crumbs on her face, and tried to see him, but accidentally tuned over the table. When he said hello to her, she barely answered to him. After they ran back to practice, she barely wished them good luck. After the boys left, Akane, Hikari, and Honoka were laughing in front of Nagisa, making her feel offended and almost went away, before Honoka noticed a diamond on her neck. Nagisa returned and everyone said that it was really pretty. Akane said that she gave this to herself for her birthday. While everyone was looking at the diamond, someone with a brown coat and hat was watching them. Then, Akane gave Hikari a short break to play. The three went to the playground and kept talking about the diamond. Mipple said that she would have like to have one, and Mepple said that he would give her one someday. They got into love-love mode, but suddenly returned to their commune forms, sensing a stalker. There is a hidden figure in the brown coat and hat, asking if they are really Pretty Cure. The girls were prepared to fight, but the figure kept asking the same question. Then more voices came from the invisible figure and he then took off his coat. It appeared there were many things inside said coat and started attacking Nagisa, Honoka and Hikari. The girls transformed into Pretty Cure and Shiny Luminous. They defeated those things, but it appeared to be normal frog mascots with elastic arms. They revealed themselves to be that they were testing the Cures because they wanted them to protect their home world, the Garden of Hope. They explained their story about the Dark Witch, trying to thief their precious Diamond Line. Mipple, Mepple, and Pollun said that it's probably something similar to the Garden of Light's Prism Stones. They will help them; however, Hikari notices Akane was going to be really busy today. Then Honoka's grandma came, and they had to hide everyone in the closet. She asked to take off the laundry because it's going to rain.
Later, the mascots kept asking them to come right now. They said, that they'll give them charms - the proofs of courageous warriors in the Garden of Hope, which were diamonds. Pollun asked them to go, because he wants to see it. Everyone asked, and Nagisa accepts their invitation. The mascots took the girls outside and used their diamonds and a chant "Kaeru Pyoko Pyoko Mi Pyoko Pyoko, Awasete Pyoko Pyoko Mu Pyoko Pyoko" to transport the girls into the Garden of Hope. The girls were in a huge diamond, and the whole Garden of Hope was one huge diamond-shaped planet. When they landed, Mipple, Mepple and Pollun were unconscious. Then Nagisa saw a lot of diamonds outside. Honoka was impressed, and Hikari was worried, because she has to help out at the cafe. Nagisa asked, where is the Diamond Line, and Marquis proclaimed that it's at the end of the road. Nagisa asked will they fly, but Round protested that they can use this only to travel outside the Garden of Hope: to walk, making everyone fed up. Meanwhile, the bat Zakenna informed the Dark Witch, that Pretty Cure and Luminous came to the Garden of Hope. The girls finally reached the palace. They entered inside, and heard something. Marquis notices that it's probably the Prince of the Garden of Hope, practicing his swordplay. Nagisa reacted bewildered and surprised that the Prince looks identical to Fujimura Shougo, while Honoka and Hikari remain neutral.
Later, the mascots presented the girls the protector of the Fountain of Hope, the Kero Kero God, which is a frog monument. Then the girls entered the palace and met the Queen of the Garden of Hope. The Queen congratulated the girls, and her butler showed girls the Diamond Line - a bracelet, a pendant and 2 earrings made from diamonds. Today is the only day in the year that Queen wears it, which is her birthday, and it gives hope to all the worlds, and if the Diamond Line is stolen, then all the hope is lost and all the worlds (including Garden of Rainbows) will be deserted in darkness, before the trio agreed to help them. Later, when the mascots told girls about the party, Square opposes the Cures' help, and proves that the warriors should be protecting the Diamond Line, and now walks away.
Later, the mascots told girls about the party, and Pollun awakened. He met Marquis and they became friends. Honoka follows to talk with Square, but when they tried talking, he just ran away. Later, all 3 girls got in dresses for the party. Then Square started making fun of them, that they can't work alone, only by combining their powers. Nagisa got furious at him and ran away, which makes Mepple follow her. Then the prince came, and asked, did the witch already came. Honoka lied, that she went to patrol outside.
Meanwhile, everything started and the Queen came out wearing the Diamond Line. She blessed the diamonds of the citizens, and went outside. Dark Witch interrupted the celebration and begins to attack with her Zakenna, formed into a pirate ship. The knights tried battling her, and she transformed front of her ship to shark Zakenna. Without Nagisa, Honoka and Hikari could just watch. Then Hikari transformed to Luminous to fight until Nagisa comes, but she was beaten by one shot... The witch triumphantly stole the Diamond Line from the Queen, according to the Dark Witch, she is one of the servants of the Dotsuku Zone, and her goal is to resurrect the Evil King with the Diamond Line, since all the world will be imbalanced. Luminous halted her, but the witch knock her unconscious. Nagisa finally arrived to transform to Pretty Cure. They tried fighting back, but they become flimsy, before the Dark Witch disappears. Everyone, especially Square, blamed Black, but Mipple and Mepple defend her. Sadly enough, Black just apologized to everyone and went away crying.
Black was crying in the balcony, when the prince came. He said, that it's not only her fault. No matter how much he practices swordplay, in the end he just didn't had enough bravery to fight. He forces Black to retrieve his clover charm for protection. Then Black was walking the hall when White called her. They decided to go and take back the bracelet. Everyone (except Square, who was still thinking of them as burdens) seemed to be forgiven Black. Without the Diamond Line, the Fountain of Hope started parching, and the Garden of Hope started being wrecked too. Then everyone flied to the place where the witch is with the same spell. The prince tried to follow them, but he couldn't travel without his charm.
The gang reached the ship graveyard - place where the witch lives, and her bat Zakenna broke the diamond, making them fall. White had to save Black from falling, because she can't swim. Everyone were fighting these bats. One was about to defeat Pretty Cure, but the witch eliminates it, pondering that the bat was rather weak; now, she prepares to battle the Cures. Square tries punching her with his elastic abilities, but she moved quickly and used a move on Square. Pretty Cures decided to use Marble Screw Max, but the witch dodged the move with her gigantic dark element. Now, every ship was set ablaze. The girls tried to save everyone, but Marquis was missing, and Round finds his torn cape. Square blamed Pretty Cure, but everyone else said, that it was the witch's fault. Then the charms reacted to the bracelet in order to discover Marquis.
In the Dark Witch's lair, something was shining in the witch's feather collar. It was Marquis hiding behind her. The Cures were fighting against the bats to proceeded to the witch and steal the ball from the Dark Witch. Pretty Cure were battling the witch, while the mascots carried the bracelet into the Garden of Hope, and started carrying it to the palace.
Meanwhile, Hikari awakened in her room and saw what was left from the Garden of Hope. Pretty Cure were battling the witch, when Black remembered, that today is a sale at chocolate store, and because of that witch she won't get in time to buy them (that won't be important to this plot, though). They almost defeated the witch, but she fired her move right in front of the girls' faces, knocking them unconscious. Then Marquis came out of the ship to the Black, and the witch flew back to the castle to take back the bracelet.
The prince wields a horse to help the knights, and took the bracelet. Hikari came too, and together they carried the bracelet to the palace.
Marquis cried for Pretty Cure. He said the spell, but nothing happened. He started crying again, but the charm the prince gave to Black reacted.
The witch sent her bat Zakenna to fight the frog mascots, while she herself headed to palace. The Prince and Hikari got to the palace, but at the same time the witch quickly appeared before them. The Prince trembles as he tries to keep the witch away with his sword, facing his fear. The Dark Witch fires at the prince, but Hikari sacrifices herself and jumps in front, making her pass out. Black and White gets mad and stand up to fight. The witch summoned dozen of Zakennas, but Black and White defeated them with one blast. The witch transformed into her true form and started attacking the Cures. The girls were weakened, but still stood their ground. White said, that for them to lose is "Really unbelievable!". They stood up, with Hikari still unconscious. The Queen now regenerates and commands everyone to give their powers to the girls. They have to believe in the cures and the diamonds. Everyone stood in circle around the Cures, and gave them powers. Hikari woke up transformed to Luminous. The Dark Witch directs her attack at all of them, but Square jumps in front, barely staving off the attack.
All the frogs, including Square, gave the girls their charms. Their Cure outfits changed to gold colored, and they gained the ability to fly, faster than the witch. Then Marquis remembered the Dark Witch's soft spot: her stomach. The Cures used the golden version of Extreme Luminario, and overpowered the witch.
The Garden of Hope and the Fountain of Hope returned to normal. The frogs, especially Square, don't want them to leave, but after a tearful goodbye, the girls finally return back home.
During their short trip back through space, Honoka asks Nagisa if she is sure she don't have any regrets, to which Nagisa reluctantly answers that she probably should have accepted one of the diamonds they were offered as a reward. Back home, Hikari hurries to apologize to Akane for being late for her shift, Akane looks at her surprised, saying that Hikari's break has not ended yet, leading Hikari to realize that during the time they were gone, almost no time had passed in The Garden of Rainbows. When it starts to rain Honoka suddenly remembers that she forgot to take down the laundry she like she promised her grandma earlier. When she hurries to take it down, she sees a frog in the grass and tells Nagisa to come look. Honoka claims that it's the Kero Kero God, whereupon Nagisa suggests they to try to fly, just the two of them. It doesn't work, and the girls start laughing.
Movie Exclusive Characters
- Queen of the Garden of Hope
- Prince of the Garden of Hope
- All of the names of the frogs are names of precious stones or types of cuts made to these stones.
- "Kaeru Pyoko Pyoko Mi Pyoko Pyoko, Awasete Pyoko Pyoko Mu Pyoko Pyoko" is a famous Japanese tongue twister, translating into "Take two sets of three frog croaks, add them together and make it six croaks".
- In the 2nd trailer, Cure Black and White's earrings are miscolored as platinum, instead of gold, from their original season.
- The movie's theme, Akane suddenly buying herself a diamond necklace, and the whole group's (Nagisa's in particular) odd interest in diamonds are explained by this movie being sponsored by a group of jewelry manufacturers and stores (as seen in the ending credits at about 1:10:03). The Diamond Line is named after a set of jewelry produced and sold by them.