This is the first episode in which we are introduced to a second Sailor Warrior, Sailor Mercury. It begins with Queen Beryl telling Jadeite that she heard that there are mothers in Japan who push their children academically. Of course, she wants to harness all the energy that comes from these children. There is a slightly humorous moment at the end of the conversation where Queen Beryl and Jadeite both realize that they don't know what happens to the children after they graduate from school.
Usagi is reading a comic book at home when her mother comes in and asks her how she did on a mock exam yesterday. They have a conversation about Usagi's bad grades, and Usagi makes the excuse that if someone is in first place, someone else also has to be in last place. Usagi returns to her room, supposedly to study. Luna starts lecturing her about finding the princess they are supposed to be looking for, but is dismayed to find Usagi looking at a comic book again.
Late at night, Luna goes into the arcade (the same one Motoki works at) and logs into a Sailor V video game screen with codename "Luna" and passcode 0091. Her secret password is "the rabbit on the moon makes rice cakes" (This is a play on words since Tsukino Usagi's name translates to something like "moon bunny".) The computer screen replies with "The rice cakes are sticky" and Luna says "When I grilled them, they puffed up." Convinced of Luna's identity, the entity on the computer screen asks if she has located the princess yet. It also tell her about a new energy contained in a girl that could be a monster. Luna agrees with this theory.
At school, Usagi, Naru, Umino and the short fat girl they hang out with sometimes notice a new student in the hallway, Ami Mizuno. Rumor has it that the new girl attends an expensive cram school on a full scholarship and that her mom is a doctor. The students theorize that they must be rich, but immediately write Ami off as being stuck up and having a bad attitude. Ami seems to hear them talking and Usagi tries to quickly change the subject.
On her way home, Usagi comments to herself that it must be nice to be as smart as Ami and that she is always worried that her mom will kill her for her bad grades. Suddenly Usagi sees Ami walking down the street in front of her. Before she can reach her, she sees Luna about to tackle Ami from a high place. Luna jumps on Ami's back and scares her, but all Ami does is pet Luna and say she is a nice cat. Luna thinks to herself that she senses a strange energy coming from Ami, but she doesn't know what it could be. To diffuse the situation, Usagi calls Luna over to her and apologizes to Ami. Ami asks Usagi is Luna is her cat, and says that since she came from the sky she thought she was an angel. Usagi and Ami finally become properly introduced, and Usagi thinks that Ami might be able to help her study for exams. Usagi invites Ami to go to the arcade with her and Ami agrees. Usagi shows her the Sailor V game and tells her she will be very good at it if she can get over 500 points on her first try. Ami turns out to be a natural at the game, scoring over 30,000 points immediately and beating the high score on the machine. A crowd gathers to watch her play, but Ami suddenly realizes that she will be late for cram school and quickly rushes off.
As Usagi leaves the arcade, Motoki comes out and hands her a floppy disk that Ami dropped. This is kind of funny because it really shows the series' age. The disappointed Usagi (hoping he had something more to say to her) agrees to bring the disk back to her. At cram school, Ami realizes that she is missing her floppy. She is approached by the teacher who tells her to study hard using her "Crystal Disk" and that she can't afford to be lazy since she is on a scholarship. Ami says to herself that the disk gives her a headache.
Usagi manages to find the cram school, but she is approached by Mamoru, who teases her about studying. Mamoru asks if the cat with Usagi was just talking. Usagi tells him that of course cats can't talk and runs away. Luna tells her it would have been big trouble if he found out. Usagi realizes that since they were in such a hurry, she forgot to return the disk. Luna suggests that they check out the contents of the disk because she finds it suspicious. Luna puts the disk into a computer and activates the program, since Usagi does not even know how to use a computer. The floppy disk contains Jadeite's voice telling students to offer their energy to the great ruler and become their loyal followers. Realizing that it is a brainwashing program, Luna concludes that Ami must be a monster. Usagi uses the Disguise Pen and transforms into a doctor who works at a university hospital. She bursts into the cram school, saying that she heard someone is sick in the building. She tells the students to get away from the computer screens, but they all look up at her like zombies. Ami stands up and tells her not to interrupt their studies, being the only one not affected since she left her Crystal Disk behind. Usagi yells that Ami must be a monster, but Ami doesn't seem to know what she is talking about. Luna tells Usagi to transform into Sailor Moon, which she does. Unusually, she does this right in front of Ami. As Ami looks on incredulously, her teacher comes up behind her and clamps a clawed hand over her mouth. Realizing that the real monster is the teacher, Sailor Moon gives her speech. Undaunted, the monster asks her why apples fall from trees. Usagi cannot answer correctly and the monster calls her an idiot. She attacks Sailor Moon with sharp pieces of paper she throws at her. The monster asks her to describe gravity in 50 words or fewer and Sailor Moon says that's impossible. Suddenly the crowd of possessed students attacks Sailor Moon and she is trapped in a corner as the monster attempts for force Ami to look at her computer screen. The monster realizes that Ami did not bring her Crystal Disk with her and admonishes her, but Ami says that people should study on their own without using machines. As the monster presses Ami's face against the computer screen, a strange symbol appears on her forehead. Luna sees the symbol and realizes that the strange energy she sensed from Ami actually meant that she was one of the Sailor Warriors. She jumps up in the air, does a flip, and makes a blue transforming pen appear. The monster says that she will take Ami's brain since she cannot have her energy and transforms her arm into an axe. Luna pushes the pen towards Ami and tells her to yell "Mercury Power Makeup!" Ami transforms into the second Sailor Warrior, Sailor Mercury. She uses her Bubble Spray attack to confuse the enemy in a fog so that Sailor Moon can use her Moon Tiara Action attack and defeat the monster. The students go back to normal and Luna apologizes for mistaking Ami for a monster.
Usagi hopes that having the new Sailor Warrior on her side will lighten her workload.