Chibi-Usa falls into a coma after coming down with a mysterious fever. Usagi and the others are at a loss for what to do, when a Sailor Guardian calling herself Sailor Pluto suddenly appears before them.
Ami enters the World Chess Tournament, which is being held at the newly constructed Chess Tower. But Bertheir is also there, forcing Ami to transform and reveal her identity as a Sailor Guardian to the enemy.
Wiseman predicts that Chibi-Usa will appear at Hikawa Shrine. Learning of this, Rubeus orders Koan to go down there and eliminate their target.
Mamoru has a dream in which a mysterious voice warns him that being with Usagi will bring her great misfortune. Meanwhile, Sailor Moon is put into a deep coma after being attacked by a Droid.
Chibi-Usa leaves the house after being scolded by Usagi. Roaming the streets alone, Chibi-Usa is overcome with sadness and begins to cry, which draws the attention of Rubeus and the Four Spectre Sisters.
The girls enjoy some vacation time on an island. But during lunch Chibi-Usa and Rei get into a small fight, causing an angry Chibi-Usa to go out to the sea alone.
Minako and Makoto clash over their opposing views on love. Wanting to break the tension, Usagi takes the girls to check out a new accessory shop, unaware that Petz and Calaveras run the place.
Rei's grandfather is upset over the fact that Hikawa Shrine has had fewer female visitors lately. He then decides to retire as head priest to start a new business, which would allow him to be around young women, much to Rei's annoyance.
The Sailor Guardians head out into the Arctic Circle. Having anticipated their arrival, Queen Beryl sends the DD Girls, who ambush them. To Sailor Moon's horror, the Sailor Guardians fall one after another as they try to defeat the DD Girls.
Sailor Venus finds the Dark Kingdom's hideout. The Sailor Guardians fall into Kunzite's trap, which hurls them into the past. The girls find themselves in a world called Silver Millennium, where they meet Queen Serenity, the mother from Usagi's past life.
Sailor Moon and the other Sailor Guardians appear to have a falling-out. But it's all part of the plan to locate the enemy's hideout. Also, a nosy journalist named Nana Asahina, who they suspect is a monster, approaches them.
Minako receives a surprise visit from Katarina, an Interpol officer from the UK and Minako's former partner while crime fighting as Sailor V. The two solved many cases together until a tragic incident forced them to go their separate ways.
The Dark Kingdom is trying again to revive the Seven Great Monsters. With five of them already under enemy control, Sailor Mercury and Jupiter scramble to protect Ryo Urawa, while Moon, Mars and Venus stay behind at Hikawa Shrine to protect Grandpa Hino.
Usagi goes on a family vacation to the hot springs, where she is unexpectedly reunited with Mamoru. But due to the Dark Kingdom's brainwashing, Mamoru no longer remembers Usagi or even who he really is.
Olympic figure-skating gold medalists Janelyn & Misha offer to coach groups of five girls. Usagi and her friends decide to investigate. Makoto, a master skater, gracefully glides across the ice and soon begins to receive personal lessons from Misha.
Usagi and her friends go to a ski resort to participate in the Moon Princess Contest, unaware that it's part of Kunzite's plan to eliminate the real Moon Princess. During the ski contest, Usagi and Rei end up falling for the trap.
Usagi decides to take the Princess Seminar course at Rose Mansion to become more princess-like, and the other Sailor Guardians join her. But unbeknownst to them, this seminar is actually a trap set up by the Dark Kingdom to find Sailor Moon.
Usagi is haunted by dreams of Tuxedo Mask, who has been abducted by the Dark Kingdom. Minako takes Usagi to a popular hair salon in the Juban District, hoping it will help take her friend's mind off of her recent worries.
Tuxedo Mask is fatally wounded while protecting Sailor Moon. Responding to Sailor Moon's tears, the seven Rainbow Crystals gather to form the Legendary Silver Crystal, and she is transformed into Serenity, the Moon Princess that everyone has been seeking.
Now that Sailor V (Sailor Venus) has joined the team, all of the Sailor Guardians are finally together! Zoisite has discovered that Tuxedo Mask is actually Mamoru Chiba and challenges him to a showdown for possession of the Rainbow Crystals.