A man stands under a large satellite dish. A small crystal falls from the sky into his hand.
Michiru examines her reflection in the mirror. She doesn't like her new lipstick. Setsuna assures her that the color is fine. As they're talking, the image of a comet appears in the Aqua Mirror. Haruka interrupts them, showing them a clock. They're already late for Makoto and Minako's joint birthday party. [Minako's birthday is in late October and Makoto's is in early December. They must have celebrated both birthdays in November.] They catch a taxi and speed away.
The Inners chide the three for being so late. They start to have a toast to the two birthday girls, but Chibi-Usa feels that something is missing. At that moment, the cats walk in. Luna blames Artemis for their tardiness because he was late in picking her up at Usagi's house. Artemis resents that because he always has to pick up Luna; she never goes to visit him. "You're bickering like a married couple!" Minako complains.
Mamoru pops the cork on some champagne and everyone lists his/her glass in a toast. Outside, snow begins to fall.
A few days later, Luna goes for a walk by herself in the snow. She thinks back to Minako and Makoto's party. Minako had teased Luna, saying that Artemis treats her like a queen. Even Mamoru had gotten into it, saying that Artemis would be thrilled if Luna visited him one in a while. So, today Luna is going to thrill Artemis by visiting Minako's house.
The main reason Luna has never gone to "Art's place" is because she has to cross a very large and busy street. The last time she crossed it was the day she met Usagi and those kids had placed a Band-Aid on her crescent moon, disabling her powers.
Just as she crosses the street, some kids spot her. Luna jumps on a brick wall to avoid them, but the kids grab her by the tail and pull her down. Of course, they are transfixed by her crescent moon bald spot and decide to affix a Band-Aid on it. Luna squirms and runs away, her powers useless. She wanders into the street, and a car barrels towards her. "Oh... Before I die... For once... If I had gone to meet Art..."
Luna opens her eyes and finds a handsome blonde man staring down at her. He explains to her that he, Oozora Kakeru, saved her from the car. She wasn't hurt much, just a scrape on her arm, which he tied with his handkerchief. He takes off the Band-Aid and gives her some rice sugar candy in the shape of stars. He leaves her for a meeting, and Luna listens from Kakeru's office.
Apparently, Kakeru is employed by a space agency as a researcher. His childhood friend, Nayotake Himeko, is planning on being the first Japanese woman in space and the youngest female astronaut at 22. [Note: Oozora Kakeru means "heavens" and "to soar; to fly." Hime, which is what Himeko is called, means "princess."] The other workers talk about Kakeru's many comet discoveries, especially his most recent. He saw a comet that appeared to come from the Moon. Because of its origin, Kakeru named it Princess Snow Kaguya after a mythological princess said to have lived on the Moon.
At the age of 12, Kakeru launched a pencil rocket that flew 300 km into the air. He then went on to earn Ph.D's in American universities for space aviation, engineering, chemistry, physics, biology, and medicine. He was supposed to be the first Japanese astronaut on the space shuttle. No one knows why he wasn't chosen, and no one knows why he never tried to become an astronaut again.
Luna leaves the building and goes to the window of the room where Kakeru is in a meeting. She hears that Kakeru's comet is on a collision course with the Earth. She runs home to tell the girls about the danger. Ami says that "the probability is one in a million" of a collision occurring. Michiru checks her mirror and sees the comet fading away. They all deduce that Princess Snow Kaguya has burned up in the atmosphere.
Pleased that the Earth is out of danger, Luna goes back to return Kakeru's handkerchief. Kakeru takes her back inside his laboratory. He is upset that the comet has burned up because he really wanted to see it. Surprised that Luna has such good manners to return his handkerchief, he tries to guess her name. Luna thinks he's a real gentleman. "Kuro [Black]?" he asks. "Mike? Tama?" In order to help him out, Luna jumps on a book and points to a picture of the lunar rover. "Huh? What? The lunar rover? Luna! You're called Luna!"
"Amazing," thinks Luna. "We communicated!"
Luna sees a crystal in a petri dish that looks like the Ginzuishou. Kakeru explains that he things that the crystal is a piece of Princess Snow Kaguya. Himeko stands in the doorway and gently scoffs at him for dreaming about princesses even though he's nearly 30 years old. She says that everyone calls him "the spaceman" because his head is always in the clouds. She leaves for a meeting, and Kakeru starts to follow her. Suddenly, he gets dizzy and nearly collapses. Luna is concerned, but Kakeru says that he always gets dizzy when he stands too much. He takes the yellow ribbon from the bag of rice sugar stars and ties it around Luna's neck. "Come see me again, Luna."
A few days later, Usagi wonders aloud if anyone's noticed that Luna's been acting strange lately. Diana and Chibi-Usa have noticed: she doesn't talk much and eats nothing but rice sugar stars. Ami's also a little concerned; Luna has been borrowing her books. Artemis is the most concerned and the most suspicious of that yellow ribbon Luna has been wearing for the longest time.
Kakeru inspects the enlarged crystal in the petri dish. It has grown a lot these past few days. He thinks that, if the crystal came from the core of the comet, it can help solve the mystery of the birth of the solar system. Luna looks up and sees that Kakeru has fallen asleep at his desk. She pulls a blanket over him and walks home.
On her way home, Luna sees Usagi and Mamoru standing outside the Tsukino house. They kiss before saying goodnight. Luna just stares.
That night, Luna asks Usagi what she and Mamoru talk about. "Mamo-chan always reads these hard books, so I can't match him," she says. "I'm the only one that talks. Then he falls asleep on the sofa." Luna thinks that Kakeru is just like Mamoru.
"They way Mamo-chan looks when he's asleep, it's like a child!" Usagi goes on. "It's so cute!"
"Oh, I know!" says Luna, forgetting herself. "Doesn't it?" Usagi asks if Luna is talking about Artemis, but Luna denies it. Usagi doesn't quite believe her. "Say, Usagi-chan," Luna asks. "What does k... kissing taste like?"
Usagi is caught off-guard. "Well, it tastes... sweet."
Later that night, Luna watches Kakeru eating rice sugar stars in his office. Himeko tells him to stop eating so much sugar and to go home, since it's already 11 PM. He agrees, but gets another pain. Himeko is very concerned and says that he keeps getting dizzy because he doesn't take care of himself. She then says that he couldn't become an astronaut because he didn't take care of himself. Kakeru gets a little angry and says that it’s his duty to observe space, and he asks if Himeko is going back to America. She turns on the television to the late-night news. The current story is about the newly chosen space shuttle crew. Himeko is not a member.
With tears in her eyes, Himeko says that she was dropped. She'll go back to America and try again. "Just because I was dropped once, I won't give up. I'm not like you. I don't forget my dreams!" She runs from the room. Sorrowfully, Kakeru picks up Luna and takes her home with him.
Kakeru looks in his refrigerator for milk for Luna. He gets another pain and asks Luna for his medicine. On the coffee table, there are countless packets of pills and powders. Luna brings him a few and Kakeru washes them down. Luna wishes Ami and Mamoru were with her because they could figure out what is wrong with Kakeru and how much medicine he should take. Kakeru falls asleep on the couch.
The next morning, Kakeru wakes up to see that Luna spent the night watching over him. He says that he would like to show her a sunrise from space. He falls back asleep. Luna creeps up his chest and kisses his lips. She runs out of the building.
When Kakeru wakes up again, Luna is gone. He reads an old postcard from Himeko. He decides to take some vacation time.
Luna goes back to Kakeru's office, but he isn't there. She overhears that he has taken a trip to America to visit the Kennedy Space Center. Luna runs to the airport and flies to America on the wing of Kakeru's plane.
At the Kennedy Space Center, Kakeru is greeted by some good-natured ribbing about finally acting like an astronaut again. He walks around and spots Luna and her yellow ribbon. He is surprised and thinks that Luna's master must work for NASA. Kakeru tells Luna that he's a bad person because he was happy when Himeko was cut from the crew. He thinks back to the days when he and Himeko were children.
The young Kakeru wanted to be an astronaut. Himeko, too, said that she would be an astronaut so she could see if Princess Kaguya really did live on the Moon. They made a pact to become astronauts and to go to the Moon together. Now, Himeko is mad at him. Kakeru collapses in pain. Luna runs to get help and sees Himeko. She leads Himeko to Kakeru.
The doctor tells Himeko that Kakeru has arrhythmia. He advises them to get back to Japan and have Kakeru hospitalized. He can never be an astronaut.
Luna tells Ami about Kakeru's illness and brings samples of his medicine. She says that one medicine must be digitalis, a diuretic that thins the blood. Another is verapamil, a drug for heart disease.
Everyone is gathered together. Minako announces that she thinks Luna's in love. Artemis is devastated. Everyone has noticed it except for Artemis. Minako urges him not to take Luna for granted. Even though they have Diana in the future, the future can easily change. Depressed, the white cat leaves.
With Artemis gone, the girls can talk without worrying about hurting his feelings. Makoto, Minako, and Rei remember their old loves and lament how horrible it is to be alone on Christmas. Michiru says that she understands how terrible lonely Christmases can be, and she rests her head on Haruka's chest. As they all talk, a spirit peeks in through the window, watching them.
Chibi-Usa remembers how she celebrated Christmas in Crystal Tokyo with her parents. Each Christmas, they picked someone to be the Christmas star. The star would get the present he/she wanted most. One year, Chibi-Usa was the star, and she received Diana as a present.
Himeko calls Kakeru on the phone and tells him that she made the arrangements for him to check into the hospital. He says he'll go after he stops by his office. When he enters his office, he sees that the petri dish containing the small crystal has shattered. In its place, there is a large crystal with the figure of a woman inside. Kakeru is amazed and begins to feel a pain in his chest.
Kakeru is taken to the hospital. As he lies in bed, the spirit enters the room, bringing the cold air with her. "You have gotten the first piece of me," she tells him. "I am Snow Kaguya. I was named by you." Kakeru thinks that she is an incarnation of death and tells her that she can take him whenever she wants because his parents are already dead and there is no one who will grieve for him.
A nurse and Luna walk into the room to check on Kakeru. He is unconscious and Kaguya is hovering over his body. Luna runs to get Usagi's help. She tells Usagi that an enemy has appeared at the hospital. Once there, Usagi uses her pen to transform into the director of the science board so she and Luna can enter the coronary care unit (CCU). Once in Kakeru's room, she transforms into Sailor Moon. She uses Moon Spiral Heart Attack, and Kaguya retreats.
Himeko hears the commotion and rushes into the room. Sailor Moon tells her that Kakeru was attacked. Kakeru opens his eyes and sees Himeko. He tries to tell her about the crystal and Kaguya, but he slips back into unconsciousness.
Outside the room, Himeko tells Sailor Moon about the crystal and the comet. She thinks that Kaguya was only a hallucination, but Luna corrects her. Himeko is shocked that Luna can talk, but Luna just continues. She says that Kaguya is an invader from the comet. As Himeko and Luna talk, Sailor Moon thinks that Kaguya might be threatening the entire planet. She then realizes that Kakeru could be the man Luna is in love with.
Michiru uses her mirror to locate the comet. Together with Setsuna and Haruka, she transforms and transports into space. The three Outers confront Kaguya, but she attacks and forces them back to Earth to the Command Center. Haruka warns Usagi that the comet is getting closer.
Back at Japan's space program headquarters, Himeko is in shock that Kaguya is an alien invader. She worries about Kakeru's safety. A man interrupts her thoughts and tells her that they just received a call from NASA. The objective of the upcoming shuttle mission has been changed and Himeko has been selected to be on the crew.
Watching their respective televisions, Usagi and Kakeru watch the announcement that Himeko is going into space.
In his dreams, Kakeru calls out for Himeko and Luna. He doesn't want them to leave him. Kaguya hovers over him. He wakes up to see Himeko looking at him. He tells her to hurry and go to American so she can finally be an astronaut. She responds that she wanted to check on him first. "I don't have long," Kakeru says. "I know it."
Tears fill Himeko's eyes. "When I come back from this flight, no matter what anyone says, I'll be with you. I'll stay with you, and fix your heart, and once more..." She sniffles. "Next time we'll go to space together. Then together, we'll find out if Princess Kaguya is on the Moon." He hugs her, and Himeko promises to take him to space one day. Kakeru kisses her and lays her down on his bed.
Luna watches in shock from the doorway. She turns towards the Game Center. Tears fall from her eyes as she wishes she was a human girl.
The shuttle is scheduled to launch on December 24th. Two days before, it is announced to the public that the new mission is to destroy the comet.
Himeko goes into Kakeru's office to get the crystal as he asked her to. She looks at the mass and decides that it is evil, just like Kaguya. She smashes it on the ground. As she leaves, she sees Luna and Sailor Moon waiting for her. "Princess Snow Kaguya is formidable," says Sailor Moon gravely. "But leave it to us." The Senshi stand in the background.
Kaguya rises out of the shards of crystal. She freezes Tokyo Bay and calls up her snow dancers. She sets the spirits loose on the city. People are encased in ice. Artemis locates a ice tower in the sea, and the Senshi rush out.
Once again, Kaguya appears to Kakeru. She wants him to rule a frozen Earth by her side. The Senshi show up in time to confront her. "I was supposed to dominate this star system," Kaguya laments, "but the solar system considered me a heretic and expelled me." Kaguya sends her snow dancers after the Senshi, trapping them in ice and filling their heads with dreams.
In the hospital, a nurse finds Kakeru's unconscious body and calls for help.
The news reports that magnetic storms are preventing the space shuttle from launching. Luna is distraught, worrying about both Kakeru and Himeko. Artemis tells her to go do what she feels she must. She runs from the Command Center.
Himeko sits in the shuttle, impatient to launch. The other astronauts laugh and ask her if she's scared. "I am scared," she says to herself. "But, Kakeru, I want to show you this flight."
Luna runs to the hospital and peers into the window. The nurses see her, but are hesitant to allow a cat in the CCU. Kakeru opens his eyes and begs for her to be allowed in. Luna jumps up on the bed and stares at the oxygen mask covering his nose and mouth.
The Outers break out of the ice using the powers of their talismans. Tuxedo Kamen and Sailor Chibi-Moon do a combination attack, Pink Sugar Tuxedo Attack, and destroy the snow dancers. The sky clears, and Kaguya heads for the full moon. Sailor Moon powers up to Super Sailor Moon and follows. She levels the heart moon rod at Kaguya and uses Rainbow Moon Heart Ache. Kaguya recognizes it as the power that drove her away from the Earth 4-and-a-half-billion years ago. She shatters in a burst of light.
In the shuttle, Himeko sees the light from Kaguya's destruction. She remembers Sailor Moon's words. The shuttle mission is reverted back to the original aims, and the shuttle lifts off. Luna watches the launch on television. Again, she wishes that she could be human so she could help Kakeru get better.
Sailor Moon meets up with Tuxedo Kamen and Sailor Chibi-Moon. They all look at a sad Luna. "This year," Chibi-Moon says, "the Christmas star is Luna." Sailor Moon holds up her Chalice and uses its power to grant Luna's most precious wish: to be a human girl. The cat becomes a girl with wavy black hair in a yellow dress.
Sailor Moon smiles. "This is your Christmas present from us. Go to Kakeru-san."
Kakeru opens his eyes and sees the dark-haired girl watching him. He addresses her as Princess Kaguya, and Luna does not correct him. She takes his hand and they float into space. Kakeru sees the sun rise over the Earth and says that he can now die in peace. "But you have to live," Luna says. "When your real Princess Kaguya returns to Earth from the Moon, you must meet her at the light of your home." Luna admits to herself that Kakeru and Himeko belong together.
Looking at the girl, Kakeru sees the crescent moon still on her forehead and the yellow ribbon around her neck. He recognizes her as the black cat that's been following him all these days. He starts to say her name, but Luna kisses his lips. "You came to see whether or not I was on the Moon," she says, still playing the role of Princess Kaguya. "I love you, my spaceman." Kakeru promises that he'll come to space again to watch the sunrise.
In the hospital, the doctors rejoice because Kakeru has miraculously come back from the brink of death. His EKG is now perfectly normal. Silently, he thinks of Luna.
Floating in space, Himeko thinks of Kakeru as she watches the same dawn he watched with Luna. She touches her belly and vows that the three of them [Kakeru, Himeko, and their child] will one day visit the Moon together.
Luna is back in her feline body and back on Earth. She takes off the yellow ribbon and carries it towards home. Artemis meets her all covered in snow. She asks if he's been waiting for her, and he answers with an "of course." The two cats smile and vow not to be late for the Christmas party.