Bertie, known as Berthier in the original anime, is one of the Negamoon Sisters. Her powers are water based. Her assumed Counterpart is Sailor Mercury.
In the anime
After Catzi left the Negamoon family, Rubeus sent Bertie to take over a crystal point in a chess building. Amy encountered Bertie and transformed into Sailor Mercury to fight her, revealing her true identity to her. Bertie retreated from the battle and entered the chess tournament where she faced Amy in the finals. Although Amy won, Bertie trapped the other Sailor Scouts in a ball of ice and started another game of chess with Amy, except this one was with her own rules - whenever Amy lost a piece, a part of her body would freeze. The spell was shattered by Tuxedo Mask, who freed all the Sailor Scouts and Bertie's plan was foiled. Avery and Prizma had appeared to reclaim some of the credit when Bertie had the advantage but explained that Rubeus was going to kick her out for her failure and abandoned her. Bertie, alone and out numbered, broke down and attempted to freeze herself to death. Catzi convinced her stop and change her evil ways so Sailor Moon used Moon Crystal Healing Activation on her.Bertie was later captured along with Catzi by Avery and Prizma, in an attempt to turn them evil again but in the battle that followed, Rubeus ditched Avery and Prizma and they were also healed of their evil. Bertie is the second of the Negamoon Sisters to turn good. In the english adaptation, Bertie is the youngest of the four sisters, however in the original japanese version she is the third eldest; Catzi being the youngest.
Aside from using Nega-energy to contaminate Crystal Points in Tokyo, Bertie can attack by firing a blast of water that could freeze a target upon impact. This attack was similar in appearance to Sailor Mercury's Shine Aqua Illusion attack. In the Japanese version, this attack was given the name Dark Water. In "Checkmate", she used a more advanced version of the attack that was suicidal and had the effect of freezing most of the surrounding area as well as Bertie herself, which was called Dark Water Full Power in the Japanese version.
- Bertie is one of three Sailor Moon R villains whose name is similar to a character on Harry Potter, in her case, Bertie Bott, the inventor of Bertie Bott's Every Flavor Beans. The other two are Rubeus and Avery.
Voiced by Kathleen Laskey in the English anime.