What Japanese myths/beliefs are referenced in Ponyo, and why was tasting blood relevant?

Question

I rewatched Ponyo recently, and there are quite a few briefly touched on, but not thoroughly explained, mystical elements that left me wondering rather I was missing part of the allusions. I'm not sure which elements are simply part of Miyazaki's usual building of unique/magical worlds, and which are drawn from Japanese myth and legend that a Japanese audience would recognize but an Western audience doesn't.

The one that stood out particularly to me was when the titular character first tastes human blood early on. Her father explicitly asks if she tasted blood shortly after as if it has some major significance. The movie doesn't otherwise explain why it's significant or reference it afterwards. Ponyo also tastes ham early on and shows a love of it, which I think is just character building for her but I couldn't be certain if it was related to the tasting blood reference as something else she 'shouldn't' have eaten that affected her magically somehow?

Is there a Japanese myth or folk-tale relevant to tasting blood, or flesh? Would some or all of a Japanese audience recognize this moment as relevant, and know why, which simply didn't translate to English?

A previous question already explained Ponyo is likely a Ningyo, but why she can work magic and specifically how she is able to change into a human isn't explained so I'm also curious about that. I know Japanese culture has a number of myths about animals (most common foxes, but I've heard swans and others) that can temporarily or perminately turn human, so I imagine it may simply be a reference to that general trend in Japanese myths, but is there a specific myth about a fish turning human that is the basis for Ponyo?

There are a number of unexplained mythical elements, like who Ponyo's father is, how he works magic, why Ponyo leaving caused such an imbalance with the magic and how her being accepted by her friend somehow counteracted that imbalance. These all seem more likely original elements created to drive the story, but I'd love to hear about any folktale references that are relevant to these as well; but I'm mostly asking about how tasting blood was relevant to Ponyo's drive to, and ability, to turn human.

Answer 1

As stated in https://en.m.wikipedia.org/wiki/Ponyo, Miyazaki has said Ponyo is loosely inspired by The Little Mermaid, that is, the original Hans Christian Anderson tale. You'll notice a few of the details very specifically match the original fairy tale, like the fact that there's a possibility that Ponyo will turn to foam, as the original mermaid did.

The idea of natural balance (and people upsetting it) is a theme Miyazaki commonly uses in his movies. For example, taking the head of the forest spirit causes an imbalance with nature. Or in Nausicaa of the Valley of the Wind there's the balance of the toxic spores, the insects, and nomu.

However, I cannot say whether there was no references to Japanese mythology.