Believing the Black Moon Clan may have taken the other Sailor Senshi to the future, Usagi and Minako asks Chibiusa if she can take them to the future, but Mamoru suggests they give her some time to think it over first. As Chibiusa spends the night at Mamoru's apartment, Usagi admits to her jealousy over how close the two appear to be, but Mamoru gives her his assurance and spends the night with her. Luna recalls in a dream about a door that appeared in the Moon Kingdom that Queen Serenity forbid her from opening.
Chibiusa decides to take Usagi and the others to the future, using her space-time key to open a wormhole. However, they become separated from Chibiusa and wind up across from the door from Luna's dream, which is guarded by the Guardian of Time, Sailor Pluto. Believing Usagi and the others to be intruders, Pluto is hostile towards them until she is stopped by Chibiusa, who is revealed to be a princess.
Glad to see Chibiusa's safe return, Pluto grants the group passage to the 30th Century, where a large black crystal had robbed energy from all of Crystal Tokyo's citizens. Before they can reach the crystal palace the group is confronted by Chiral and Achrial, the servants of Black Moon's Esmeraude, who traps everyone inside a magnetic field from which they can't escape. Just then, Mamoru once again hears a voice which shows him how to break the field and defeat the brothers. Upon reaching the crystal palace and coming across Chibiusa's mother, Neo-Queen Serenity, the group are greeted by another Tuxedo Mask.