It's Rei's birthday. A boy approaches her with a bouquet of red roses. He hands her the flowers and a letter for her birthday. Rei is surprised. She doesn't have a chance to react, though, because Usagi slips around the corner and snatches the letter. She reads it and squeals that the boy wants to go out with Rei. Ami also shows up and says that Rei never told them when her birthday was. "If it was important, I would have told you," Rei says coldly. "But I don't want presents, and I have no interest in boys." This last part is unfathomable to Usagi. Rei walks away, leaving Ami and Usagi to wonder why Rei never talks about herself.
After school, Rei goes home to the Hikawa Shrine. Her grandfather tells her that her father has sent her a birthday present: white casablanca lilies and a white dress. Every year, he sends her the same presents. While she's still holding the gifts, Usagi and Ami walk in with their own present. It's a music box shaped like a tree. Rei's grandfather remarks that Rei has never received a gift from friends before.
While the girls are admiring the pretty lilies, a car pulls up to get Rei. Her grandfather explains that, every year without fail, Rei's father takes her out to dinner for her birthday. He's a busy politician and rarely sees his daughter since Rei's mother died and Rei went to live with her maternal grandfather. She doesn't get along with her father.
The car brings Rei to a restaurant called the Rain Tree. She is wearing the white birthday dress she received earlier in the day. The waiter leads her to a table where her father sits with a young man. Rei's eyes go wide as she recognizes him. "Kaidou-san!"
Kaidou compliments Rei, saying that she looks just like her mother in that dress. She sits and hears a music box playing the same tune as the one Usagi and Ami gave her. The waiter explains that, since the restaurant and the tune have the same name, the restaurant is displaying the music boxes. Rei's father asks her if she came to the Rain Tree for her birthday last year with Kaidou. Last year, Rei's father was unable to join them.
Rei thinks about Kaidou. He's her father's most trusted assistant and protege. Even when she was little, Kaidou was always around. For her twelfth birthday, he took her to a flower shop and let her pick out any flowers she wanted. Rei chose the casablancas. Later that day, Rei discovered that all her gifts had been picked out by Kaidou, not her father. Rei thinks back to her last birthday, when she had dinner alone with Kaidou. He had apologized her father's disregard for his family and offered to throw Rei and her friends a party. "I have no friends," Rei had told him, "and I don't want to make any. You can't have faith in people. I believed in Dad." Kaidou had responded that he would never want his future children to be as unhappy as Rei and that he never wanted to marry. Rei smiled a little. "We're the same. You and me. Kindred spirits."
At night, Rei sits up in bed, thinking about Kaidou. She can't forget him, which is what she really wants to do. She gets up to meditate in front of the fire, but the Rain Tree tune breaks her concentration.
As the months pass, more and more people are buying the Rain Tree music boxes. The rainy season is in full swing, and everyone is very gloomy.
Rei walks through the rain and runs into Makoto. The latter explains that the heavy rains have been negatively affecting her plants. Rei invites her into the Rain Tree so they can talk. Once seated, Rei asks Makoto about her life before moving to Juuban. Makoto says that a friend and herself liked the same boy. She had thought the boy would choose her because they were good friends, but the boy went out with Makoto's friend instead. "We're kindred spirits," Rei says mournfully.
Makoto's story has made Rei think about Kaidou again. On her way home from school one day, Rei saw Kaidou with his arm around a woman. Hurt, Rei turned and ran home to call her father. Rei's father only said that he was training Kaidou to enter politics, and that Kaidou was engaged to a political giant's daughter.
In the present, Rei asks if she can play the Rain Tree's grand piano. As she plays, people mention that she is the daughter of a famous politician. When she is finished, Rei gets up and a blonde woman takes her place. Rei wakes up Makoto who has fallen asleep, and the two leave.
The rain in Japan is becoming worse. Usagi tells her mother that the schools are closed because of all the rain and floods.
Rei arranges some flowers in a pot. She thinks it will be the perfect gift for Makoto, and that the two can talk about their broken hearts. She rings Makoto's bell, but the door is open. Inside, Makoto is sitting in a corner listening to a music box. Rei realizes that everyone has been acting strange since the Rain Tree music boxes appeared. She smashes the box on the floor and a spirit escapes. Rei transforms into Sailor Mars.
A flashback begins of what happened last year. Kaidou saw Rei run away from him and the woman. He went to visit Rei at the Shrine and gave her a book. Very straightforward, Rei asked him if he was going to get married. He responded that her father was making him, but that he won't have any children. "Liar," Rei said. "If you enter the political world... If you succeed Dad, then... I wanted you to marry me." They kissed.
All the Rain Tree music boxes shatter around the city. The blonde woman at the piano stands up. She has been manipulating the music boxes all this time in order to capture the energy of the city. She makes Sailor Mars see illusions of herself and Kaidou, her mother, and Kaidou melting into Jadeite. Sailor Mars resists, however, and throws an ofuda at the woman. She admits her defeat and retreats.
The other Senshi arrive, but the enemy has been defeated. Sailor Mars says that, if she fell in love with a person, she would want that person to be hers in every sense. Since that is not fair to the person, she will never fall in love. "I don't need love now," she tells the girls. " But I have kindred spirits with the same goal. I have you all."
The girls sit on the beach enjoying the warm dry weather. A waiter brings a drink over to Rei. Some boys sent it to her, her fifth free drink of the day. Ami, Makoto, and Usagi all sweatdrop because the girl who is not interested in boys is the one getting all the attention.