Anime

widely known in niche circles

I wouldn't say it's niche. I'd understand that about similar works like "The Pied Piper" (manga, the adaptation wasn't very good, and only the character designs remained) or "Gokudo," but not about the very famous Slayers.

24. Piece - Actually, I think I'll like it. The fact that it's an ongoing series is off-putting. If it ends, we'll revisit it.

If I remember correctly, two-thirds of it is already completed. It might end in about ten years. I think you might actually enjoy it.