Ep 19. Act.19 Time Warp - Sailor Pluto -

In "Sailor Moon Crystal" season 2 episode 19, titled "Act.19 Time Warp - Sailor Pluto -," the Sailor Scouts find themselves in an alternate timeline where the world is ruled by the Black Moon Clan. After a dangerous encounter with the clan's henchmen, Sailor Pluto appears and quickly sends the Scouts back to their own time.

However, Pluto's actions have caused a time paradox, putting her own existence in danger. She reveals to the Scouts that her job as the guardian of time is a lonely one, as she must forever stand at the gates of time and never interfere with the timeline. But she has grown to care for the Scouts and can no longer bear to watch them suffer.

Pluto enlists the help of Chibiusa, who has a deep connection with her and the power to manipulate time. Chibiusa agrees to help, but only if Pluto promises to never leave her alone again. Pluto agrees, and Chibiusa sets about creating a temporary time portal so Pluto can return to her own era.

However, the Black Moon Clan has caught wind of the disturbance in time and sends their powerful commander, Wiseman, to investigate. The Scouts and Pluto team up to try and defeat Wiseman, but he proves to be a formidable opponent.

In a last ditch effort, Pluto sacrifices herself to save the Scouts and destroy Wiseman once and for all. The Scouts are devastated by her loss, but know that Pluto died a hero and with honor. They make a promise to keep fighting against the Black Moon Clan and any other threats that come their way, in honor of Pluto's memory.