December 17, 1998
Katsuyuki Sumizawa (original episode)
Kounosuke Uda (original episode)
Wiseman talks about his evil plans and that he is only using Prince Diamond, pretending to work for him, while actually serving an entity known as the Doom Phantom. Sapphire overhears this, and his worst suspicions about Wiseman are confirmed. He steals a control chip from the reactor of the Dark Crystal to prevent Wiseman from overloading it and causing it to explode. Wiseman attacks him. Though he teleports away, he is injured by it.
Sapphire collapses in the park, but is seen by the reformed Negamoon Sisters and taken to their house to get better. Prizma initially thinks he is there to punish them for betraying the Negamoon. Avery reveals to Catzi and Bertie that Prizma and Sapphire were in love. Sapphire begins to realize how good life on Earth is, and that Diamond's goal to take over Earth is the wrong way. He goes to warn Diamond of Wiseman's treachery, though Prizma is afraid that he might be killed in the process. After Sapphire leaves, the Negamoon Sisters discuss what to do. Since Sailor Moon healed them, they have lost all their power, so Catzi calls Serena and tells her about Sapphire.
Sapphire is attacked by Wicked Lady, but the Sailor Scouts arrive and tell her not to hurt Sapphire. Wicked Lady traps them all in dark domes, but Tuxedo Mask arrives and destroys the domes. Diamond arrives, and Sapphire tells him that Wiseman has betrayed him. Diamond does not believe Sapphire. Tuxedo Mask tells him to listen, but Wiseman appears and shoots Sapphire with an energy blast.
Though Diamond tells him to stop, Wiseman blasts him again, killing him. Wiseman takes the control chip back. The bandages fall off Sapphire's head, revealing that the dark crescent moon on his head has vanished. Wiseman and Wicked Lady leave, and Diamond takes Sapphire's body and disappears. Prizma senses Sapphire's death and mourns.
- Final appearance of Sapphire and the Negamoon Sisters.
- Wiseman's evil plans are revealed proper to the audience.
- This is the second time a villain chooses to become good and dies. Though Wiseman's reasons for killing Sapphire were motivated to keep his plans a secret, he intended to kill him anyway.