|Nickname:||Beruche, Bertie, Birdy|
Berthier has a very darkly playful personality, but is shown to have great respect for all of her siblings. She is the only one shown to be upset when Kōan is purified by the Silver Crystal. Much like her counterpart in Ami, she is also a strategist and is incredibly talented at chess, though she apparently also cheats.
On her final mission, Berthier plays a deadly game of chess with Sailor Mercury, but her plan to freeze them all fails when Petz and Calaveras arrive and tell her they will claim credit for her success regardless of what it means for her. Momentarily distracted, she loses her chance at the killing blow against Sailor Mercury when Tuxedo Mask arrives and rescues her and the other Sailor Senshi. Her two older sisters then abandon her as a failure when Berthier turns to them for help.
Distraught, Berthier first laughs off her loss, but the laughter turns into tears of hopelessness and rage as she uses her Dark Water power to freeze herself and everyone around her. However, a newly healed Kōan convinces her that she is still loved and has a second chance. Berthier relents in her suicidal gambit, and allows Sailor Moon to heal her. Later, she and Kōan, along with the Sailor Senshi, are able to convince their other two sisters to join them and become normal women.