Resolution matters. Most Demon Slayer episodes stream natively in 1080p (HD). To get a true 4K version of the Mugen Train death scene, editors must upscale the source material using AI algorithms (Topaz Video AI or Waifu2x).
If you want, I can produce a step-by-step After Effects project file checklist, a short tutorial for masking specific Rengoku frames, or a settings-only cheat sheet. rengoku death twixtor 4k