Having a separate protagonist for each chapter, I feel, ended up working against the story as a whole, at least when viewed against the field of the competition. The chunin exam is a harsh field to stand on.

As I've seen noted in comments, this has something of an SCP vibe to it, which is nice. The grisly parts, especially the third chapter, are delightfully grisly, and you sell a difficult plot device fairly well. If it felt like a cohesive narrative, this might be in contention for me, but as it is, it's not quite there. Still, glad I read it.