The "Twixtor 4K" format isn't just about technical showing off; it changes the pacing of grief. By slowing down the action, the editor gives the audience more time to process the weight of the loss. We see the exact moment the light leaves Rengoku's eyes in high definition, extending a few seconds of screen time into a long, meditative experience. It turns a fast-paced action tragedy into a visual eulogy. Conclusion

Demon Slayer's Saddest Death Wasn't Rengoku – And Fans ... - IMDb