There isn’t an official season 4 of Redo of Healer as far as the available information shows; the series is known as a single anime adaptation, so “S4” doesn’t apply. The closest likely meaning is episode 4 , which is where Keyaru adds Setsuna to his group and the revenge plot keeps expanding.

What happens in episode 4

  • Keyaru’s party continues growing as he recruits Setsuna. A review summary notes that this episode centers on Setsuna joining the team and her willingness to get stronger by any means.
  • The episode also digs a bit more into the cruelty of Flare’s side and Keyaru’s revenge setup.
  • Some episode-list material describes the broader arc around Keyaru protecting Eve and pursuing revenge, which matches the show’s ongoing direction.

About the confusion

“S4 ” is probably a shorthand mix-up, because the title doesn’t have four seasons listed in the sources I found. If you meant episode 4 , the main beat is Setsuna joining Keyaru’s plan and the story moving deeper into his revenge campaign.

TL;DR

  • No official season 4 is shown in the sources.
  • If you meant episode 4, it focuses on Keyaru gaining Setsuna as an ally and pushing his revenge forward.