So I’m working on a small written project with the help of a Japanese person. And I got a correction of a sentence, with the following added at the end:
(Well, I’ve gotten a lot of corrections, but this is the one that triggered this blog post.)
So I did the Google search on “kayo particle”, and out of the list of hits, I came across one for Nugalis.
This is a Spanish-run site, apparently not updated since August 2016, going by the last News item on the site.
But it listed かよ in the Grammar section, with the explanation
(sentence-ending particle expressing doubt)
It looks like they have vocabulary collected in logical areas, like “Daily Activities”, “the House”, “Food”, as well as the JLPT levels 1-5, and the typical adverb/adjective/verb(etc.) organization.
Haven’t had much of a chance to poke around in it, but I plan to, because it looks very interesting