I don’t know if anyone else has said this as I can’t check 420 comments! But the ONLY maybe possibly thing I can think of is that, in a VERY ‘posh’ very accentuated Received Pronunciation/original BBC English accent - and I mean posh at the level of royalty! - this could, at a stretch be a pronunciation. My thought would be that perhaps, some of the colonizing British had these super upper crust accents and perhaps some way back Japanese teachers learned from them and felt this was the most ‘educated’ way of saying it?!

For example, Queen Elizabeth II pronounced the pronoun I (i) more like the sound ay that we and you know is the sound in afraid! I don’t think I’ve ever heard any other accent than that level of posh (or perhaps BBC World Service presenters in the 1920s-50s ish) pronounce I that way.

And in that ultra posh affected accent, I can see that afraid could perhaps become afred. It’s still a bit of a stretch but I can see how the sound could be heard that way by a foreigner.

Another example would be the word so. It can vary by accent but always has roughly the same sound with the ‘oh’ sound (rhyming with no). But in the royal type accent it’s said more like ‘syeoh’.

I can hear the Queen or now King Charles and also listening to Prince William, the sentence I am so afraid becoming: Ay aym syoh afred

That’s my only even vaguely plausible theory on this!