Queen Beryl reminds Zoycite and Malachite that they need all seven crystals to release the Negaforce, and is disappointed with Zoycite that Tuxedo Mask got the second crystal. Zoycite and Malachite plan for them to take the crystal from him as he goes after the other five. Beryl tells them to find the other five crystals now.
At school, Serena gets another horrible mark on her test, while Greg comes in first. Amy comes in second, missing on a perfect score by one point. Serena suspects that Amy and Greg are in love. As Serena is giving Greg a picture, her crescent moon wand reacts to him, indicating that he is the third rainbow crystal carrier. Zoycite soon discovers this using her homing crystal, and attacks him. He knows her name, and reveals that he can see into the future. He knows about the Negaverse and that he will be turned into a monster. He tries to fight her, but she uses her Zoy attack on him. As she attempts to extract his rainbow crystal, Serena and Amy arrive, and transform into Sailor Moon and Sailor Mercury to fight her off. Zoycite uses Zoy to distract Sailor Moon, and leaves.
As Sailor Mercury gets Greg to safety, he calls her "Amy", as he knows who she is. He tells her about his power, and tells her to destroy him when he is turned into a monster. Zoycite returns and extracts the yellow crystal from Greg and turns him into Bumboo. However, he still retains some of Greg inside him, and attacks Zoycite. She drops the crystal, and Sailor Mercury catches it. However, Zoycite turns him completely evil and makes him bigger. Sailor Moon and Luna arrive. Sailor Moon uses Moon Healing Activation on Bumboo, but it doesn't work, as he is too powerful and must be weakened first.
Bumboo shoots razor sharp blades shaped like triangles at Sailor Moon, Sailor Mercury, and Luna. Sailor Mars and Sailor Jupiter use Mars Fire Ignite and Jupiter Thunder Crash on him to stop his attack. Sailor Mercury uses Mercury Bubbles Blast, and says that Bumboo is weak enough now. Sailor Moon uses Moon Tiara Magic, which attaches itself to his head and shrinks him back to his normal size. Sailor Moon uses Moon Healing Activation to heal him, turning him back into Greg. Zoycite leaves, while Tuxedo Mask, who was watching, decides to leave the crystal with them.
Greg moves away again because of his father's job. He says goodbye to Amy, who gives him a picture of her before he leaves on the train.
- First appearance of Greg
- First and last appearance of Bumboo, Champion of the Negaverse
- The Sailor Scouts get the yellow crystal
- When Bumboo shoots a blade at Sailor Moon and Sailor Mercury, cutting down a tree in the process, Sailor Moon has fangs.