Sailor Moon cries out for Sailor Mars. Sailors Venus and Jupiter arrive, but they are too late. Tuxedo Kamen takes control and tells the Senshi to detransform and get out. They listen, and as Usagi is leaving, she spies Chibi-Usa. She demands to know what the girl is doing there. "Oh no, was it your allies who took Mars...." She raises her hand to smack Chibi-Usa, but Luna intervenes and Chibi-Usa runs away. Again, Usagi sees the key and the crystal.
Back at home, Ikuko-mama asks where Chibi-Usa is, but Usagi yells that she said she was going to a friend's house. In her room, Usagi degrades herself for wanting to hit Chibi-Usa.
Mamoru looks outside at the rain. Luna rings his doorbell and takes him outside to where Chibi-Usa is sitting in the rain. He brings her inside and puts her to bed, thinking that it's best if Usagi and Chibi-Usa are separated for a while.
In her dreams, Chibi-Usa talks to her mother. Her mother tells her that when the time comes, Chibi-Usa will be ready. Against the backdrop of a crystal city, a man takes Chibi-Usa's hand and tells her that Sailor Moon is undefeatable.
Chibi-Usa wakes up crying. Mamoru tries to cheer her up with a Tuxedo Kamen doll and a rose. Luna reveals to her that she is a talking cat, and Chibi-Usa asks her if she knows anything about her cat-faced toy, Luna-P. [-P is a childish and cute way of saying -chan]. When she bounces the ball, the toy says, "Small Lady." She says that Small Lady is the name her mother gave her.
When Mamoru picks up Luna-P, he sees the image of the crystal city again. He jumps back and sees the key and crystal hanging from Chibi-Usa's neck. He asks her if that's her house key, but he is secretly starting to wonder about the strangeness of this little girl. Chibi-Usa tells him that without her key, she can't go home and that her home is very far away.
Suddenly, Chibi-Usa asks: "Is this Sailor Moon strong?"
Mamoru responds that she is undefeatable. "Maybe she'll save my Mom," Chibi-Usa says as she goes back to sleep.
The next day, Mamoru, Chibi-Usa, and Luna meet Usagi before school. Mamoru tells her that he thinks Chibi-Usa came to ask for Sailor Moon's help. Usagi is not convinced and acts cold towards Mamoru. He tries to kiss her, but she pushes away, letting his kiss fall on her hair.
After school, the girls (sans Rei) go to the Command Center. Motoki tells them that they gave him quite a shock; he never would have guessed that they were Sailor Soldiers, or that their Command Center was right under the Crown Game Center. He wishes them good luck in finding Sailor Mars and goes back to work.
As they discuss the Crimson Rubeus and Sailor Mars, Ami plays a game of chess against herself. She explains that it helps her take her find off of hard things. Makoto suggests they all go back to T*A and look for clues.
At T*A, Makoto and Ami talk to a distraught Kotono. She tell them about the spontaneously combusting nuns, and voices her worries about Rei. Makoto assures her that Rei is only home sick and should be back in school as soon as she is well again. Asanuma is also at T*A that day and says that he saw the burnt corpses as well. Kotono also talks about the disappearance of the Black Moon club and the sudden increase in UFO sightings.
When Ami and Makoto leave T*A, they meet up with Usagi, Mamoru, and Minako. Asanuma watches them. "Something about those people," he says. "They're not ordinary people." Asanuma remembers when he was taking the entrance test for Moto Azabu JHS. He had met Mamoru before the test, and the high school student had shaken his hand and wished him good luck. To Asanuma, the handshake felt like "an electric shock," as if Mamoru was giving the boy strength. Asanuma passed the test.
And then, a month ago, Asanuma was watching Mamoru play soccer. One of the other players scraped Mamoru's forearm with the cleats on his shoe. Mamoru left the game, but instead of going to the nurse, Mamoru slipped behind the building. Asanuma followed, and he saw Mamoru heal the injury. From that day on, Asanuma always wondered if Mamoru was a human or an alien.
At the Black Moon's headquarters, Prince Diamaund and his brother Safir argue about the capture of Sailor Mars. Diamaund believes that Safir should stick to producing droids, while Safir thinks Diamaund is being too forcible. Rubeus ends the fight by saying that Sailor Mars has been imprisoned by the Evil Black Crystal.
A woman with a long braided ponytail wrapped around her head enters. She is Beruche, the second youngest Ayakashi sister. "Code: 002. Operation: Remove. I will get rid of the obstructing game piece, and then I'll catch that eyesore, the Rabbit."
Ami plays chess with a group of friends. She is a little preoccupied because she's thinking about what Rei had said about the enemies sneaking in. She excuses herself, saying that she has to go home. Her friends try to persuade her to enter the chess tournament, but Ami says that she might not be able to. As she leaves, her friends talk about how Ami is very modest and does not tell anyone that she defeated the Japan junior chess champion.
Ami walks into the bathroom to find a girl battling with a broken faucet. The water is spraying all over. If she listens carefully enough, Ami can hear where the pipe is broken. She walks outside to where a man is digging. She tells him that the pipe must be bent. Sure enough, Ami's right. Beruche watches from a distance.
Ami goes to the sports club where her father is a member in order to swim. She meets Naru and Usagi there. She explains to them that her parents are divorced. Her father, a painter, taught her how to swim and play chess for relaxation.
A television is on. A talk show is playing, featuring a famous dowser Miss Beruche. Even though she is a dowser, Miss Beruche is in Japan to challenge Mizuno Ami to a chess match.
Ami meets Beruche at the World Chess Tournament. Beruche says that she knows Ami is Sailor Mercury, and that she will surpass Cooan and complete her mission. Usagi and Makoto rush to Ami's aid, all three transform.
Sailor Jupiter uses Sparkling Wide Pressure, but Beruche escapes onto the street. The Senshi give chase, but the people outside turn into droids and attack. Using her visor, Sailor Mercury sees that the droids are not real people. Sailor Venus arrives and takes out the droids with her love-me chain.
Beruche lifts up a manhole and a stream of water lifts Sailor Mercury into the air. Sailor Moon uses Moon Princess Halation to kill Beruche, but Rubeus appears and takes Mercury away.