Not sure which version this artist is referring to, but most versions of ippon-datara dont eat people.(Makes me wonder why this day is considered unlucky.)

Soalner said:

Not sure which version this artist is referring to, but most versions of ippon-datara dont eat people.(Makes me wonder why this day is considered unlucky.)

From what I could gather, the unluckiness of hate no hatsuka came first, and the relationship with ippon-datara came later (as a result of its relationship with the Hatenashi mountain range and the fact that there are no passers-by at this time of the year —to not be/to be missing → nakunaru; this na happens to be the same one as in Hatenashi).

It's true that the ippon-datara is often said not to harm humans, however this page does say they do eat the travellers that go through the mountains. Now, I have no clue where this page gets their info from, nor whether it happens to be accurate to any degree, but after translating Ohayoumu for a few months, it's clear to me that Youmu-kun mostly relies on that webpage (sometimes even copying their exact wording). And, by his own admission, he does not do his due diligence in his research.

Ipoon-datara legends vary between regions, and a few versions do eat people.(I actually considered clarifying that in my original comment but couldn't figure out how to word it correctly.) I was mostly criticizing the holiday rather than bashing the authors research credits.