While Usagi cooks breakfast, she tells what the other girls have been doing for the past four years. Ami has become a researcher and doctor in America. Rei has been training in the Kyoto mountains and her spiritual powers are even stronger. Minako has become popular worldwide and is recording a song in London. Makoto is studying to be a florist. Usagi is engaged to marry Mamoru and now she’s late to meet him.
Usagi and Mamoru go shopping for supplies for the wedding, but Mamoru doesn’t seem interested in the planning at all.
Makoto is planning Usagi’s bouquet with Motoki. He mentions that Makoto is making the cake as well. As she picks out flowers, she gets a call from Usagi saying the wedding is off. The two meet over dessert at a restaurant and Usagi feels sick and runs for the bathroom.
Meanwhile, Motoki is explaining to Mamoru why he needs to help out more with the planning. Motoki asks him what he would do if Usagi told him the wedding was off, and Mamoru if it’s going to end like that, it should just end. Usagi overhears and hands Mamoru back her engagement ring.
Luna calls Queen Serenity and the queen sends an image to talk to her. The queen says that they should just let what will happen, happen. She also warns that it feels like their is a dark power about to awaken.
Luna checks out a strange happening in an abandoned warehouse. Rei comes to do the same and is injured as Kuroki Mio awakens.
Mio takes over the Kingdom of Pierrot an abandoned amusement park. She transforms the play castle into a throne room for herself and creates a small army of clown youma called Pierrots and adopts a small stuffed dog called Chappi. Then she creates two armored youma called ‘Sword’ and ‘Shield’ and a new black and pink outfit for herself.
Usagi rushes to see Rei in the hospital, but a performance of Mio begins to perform on a screen over a city square. Mio announces that she’s going to become Earth’s Queen, but to do so, she needs everyone’s energy. Then she announces that she’s sending the Pierrot’s and that people shouldn’t resist.
The Pierrot’s appear friendly at first, but soon attack. They turn on Usagi, but Mamoru appears at Tuxedo Kamen. With the two of them together, the Shitennou appear. They inform Usagi and Mamoru that their new queen calls them and kidnap the two. Sailor Luna arrives just in time to watch them disappear.
Luna informs the others. Ami runs out of the hospital and Minako makes her driver head straight to the airport.
Mio has somehow been storing the collected energy in balloons and the wailing of the trapped humans can be heard in her throne room. She welcomes Usagi and Mamoru to her castle and informs Mamoru that he’s going to become her king.
Usagi and Mamoru are chained up in a cage. The two of them bicker, and Usagi wishes that she could still transform.
Makoto paces back in forth in her apartment while Luna calls Queen Serenity. The queen tells them that the senshi must do their best and that she will handle the fact they can’t transform by sending the “Legendary Blade”. The sword is powerful, but can only be used if all the senshi’s “hearts are one.” Makoto and Luna hop in her car.
The next morning Jadeite and Nephrite come to collect Mamoru. He and Usagi both charge at them, intent on letting the other escape. Finally, Mamoru tells Usagi to run and she manages to get away.
Makoto and Luna discover the sword is atop a cliff. Ami is in a cab heading their way, but Pierrots attack and the driver runs off. Ami climbs into the driver’s seat and is forced to nearly run them over in order to escape, but the Sword Youma stands in her way. Minako has landed in Japan as well and is attacked in a parking garage, but kicks a Pierrot through a wall. The Pierrots retreat, but the Shield Youma blocks her way.
Luna and Makoto fight their way through a group of Pierrots, but they cannot remove the sword from its stand. They decide that they must need all the senshi and a group of Pierrots climb surround them.
Mamoru is dragged to Mio’s throne room. And she casts a spell on him. Usagi hides outside and discovers that Mamoru slipped her engagement ring into her pocket when he shoved her out of the cage. She remembers who Mamoru proposed to her.
The Pierrots surround Makoto and Luna, but Ami arrives just in time to save them. The rest of the Pierrots are defeated by Minako’s timely arrival. Together, and with Rei helping with her spiritual powers from the hospital, the senshi manage to pull the Legendary Blade out.
Usagi comes rushing in at the end of the wedding. Mio commands Mamoru to finish off Usagi. He throws are sword at her, but it flies past her and cuts a rope hanging a banner, which collapses over the Shitennou.
Usagi and Mamoru escape and run into the nearby woods. Before they get far, they are attacked by the Shitennou, but then another set of Shitenoout appear. After a brief moment of confusion, the real Shitennou zap their imposters.
The Sword and Shield youma appear with more Pierrots and Mamoru transforms into Endymion before all the men attack. A brief battle ensues before the Shield and Sword youma confront Endymion directly.
The youma double-team Endymion, with Shield providing defense and Sword going on the offensive. The Shitennou attempt to come to his rescue, but he orders them to back off. He finally tricks Sword into attack Shield, and then attacks the defensely Sword.
The Shitennou come over to congratulate him (with Jadeite as giddy as a schoolgirl.) Jadeite proceeds to provoke Nephrite, but Kunzite warns them not to let their guard down, just before they are knocked down by a series of explosions. Mio comes striding out of the smoke and transforms into a plant-like youma.
Mio trounces the Shitennou and Endymion, but before she can deal the final blow, Usagi comes running in. Mio tries to attack her, but Minako cuts off one of her pincers before she can. Minako raises the Legendary Blade in the air and the senshi’s henshin items appear. They transform.
The senshi attack, finally ending the battle with Sailor Planet Attack. After the battle, the henshin items disappear again.
Usagi decides the wedding is back on.
Mamoru and Usagi exit the church after their wedding. Usagi’s friends, family and the Shitennou are all there. When Usagi tosses her bouquet, Motoki catches it and asked Makoto to marry him.
Usagi and Mamoru ride off. During the credits, we see the senshi in their daily lives.