ChibiUsa tells the group that she came from the 30th century. She says that there was a huge explosion and she didn't know what she should do. Luna wonders if the other senshi are in the future. The cats tell ChibiUsa that they want to help save her mother, and Venus asks ChibiUsa to take them to the future. ChibiUsa refuses. Kamen hugs her and says that they will help her and give her time to decide what she wants to do. Moon offers to take her home, but ChibiUsa wants to stay at Mamoru's.
Mamoru puts ChibiUsa to bed, and goes to grab a cup of coffee. Usagi decides to stay for awhile, and she asks Mamoru if he likes ChibiUsa and that ChibiUsa likes him. Mamoru is surprised by this, and Usagi stops herself, realizing that she is being jealous of ChibiUsa when she should be focused on Mars, Mercury, and Jupiter. Mamoru hugs her. and they reassure each other that they will always be together and protect each other. They embrace and kiss each other.
Minako spreads out a blanket for the cats to sleep on. Artemis wonders how ChibiUsa traveled through time, but Luna is already fast asleep. She has a dream, which is actually a flashback. Queen Serenity calls out to Luna and tells her to go no further. The door Luna is headed toward is the gateway to a forbidden land guarded by a solitary guardian. The queen tells Luna to forget what she's seen and heard.
When ChibiUsa wakes up, she tells Usagi and Mamoru that she will return to the 30th century and asks for them to accompany her. That night Moon, Venus, Kamen, the cats and ChibiUsa gather together to leave. ChibiUsa tells everyone to hold on to her hand and not to let go. Then she takes the key from around her neck and opens the time passage. A ton of light floods around them, and Moon lets go of ChibiUsa's hand.
Safir senses that the time passage has opened and it is more than just ChibiUsa traveling. Demand and Wiseman want the ginzuishou and the Crystal Palace destroyed, so Esmeraude offers to carry out the mission with Chiral and Achiral.
Moon, Venus, Kamen and the cats find themselves in a dark area, and ChibiUsa is nowhere to be found. The ginzuishou glows in the brooch, and they see a door ahead. A voice tells them to stop, and Sailor Pluto appears. She says she won't allow them to pass, and attacks Sailor Moon by yelling, "Dead Scream!" Before she can continue her assault, ChibiUsa appears and apologizes for breaking her promise and bringing them along. Then she explains that she went to the past because Sailor Moon's ginzuishou might have been more powerful than the one she carries. Pluto explains that the ginzuishou has the same power at all times. She then apologizes to Sailor Moon and thhanks her for taking care of the princess. Sailor Moon is surprised to hear ChibiUsa is a princess. She opens the time door for them and the group steps in to the 30th century.
The moon hangs close in the sky. Thick fog is in the air. The buildings appear to be melted and decaying bodies are all over the ground. The city is silent. Kamen sees a black monument and hears a voice telling him not to come any closer. ChibiUsa leads them to the Crystal Palace to see her mother. On the way, everone looks around and suddenly sees walls of crystal surrounding them. ChibiUsa realizes they aren't in the Crystal Palace. Chiral and Achiral appear, revealing that they are trapped in the mirror image of the Crystal Palace. Moon tries attacking with Moon Princess Halation, but the attack doesn't work at all. Esmeraude appears and says that they will destroy the real Crystal Palace. Crystal builds up around their bodies, leaving them unable to move. Kamen hears the voice again, telling him the crystal is not real and that he must will it to break. Kamen escapes the crystal, and follows the command of the voice to get down. The crystal explodes around them. Venus uses the Whip of Love and Kamen uses his power to destroy Chiral and Achiral. Esmeraude escapes.
ChibiUsa leads the group to the real Crystal Palace, where a large door appears. They enter and walk to a room where a woman lies, covered in crystal. Moon asks who she is, and ChibiUsa says the woman is NeoQueen Serenity. ChibiUsa hears a meow and a ring, and knows it is Diana, her gray kitten. Diana runs toward a man in a suit with a long dark cape who bears a striking resemblance to Tuxedo Kamen.