im not a scalator, so im not sure, but from my own experience and well my guess,
it seems that it depends on like for the age they are aiming or more like their knowledge of kanjis, kind of thing.Sometimes, the put furigana on words that are hard to read or that are difficult/complicated words, which means, that even for japancese ppl, its hard to know how to read them, since, a lot of kanjis, have more than one way of reading. I think you will see it, if you try to read a manga aimed for lil kids, most of the kanjis (even the easy ones) have furigana while in the ones that are aimed for older people, the furigana are only added to hard kanjis or that normally (according to the author/editor), they wouldn't use.
the other reason in which they use it, its to put a double meaning (it applies eve for easy words), its a trick the (japanese) authors use a lot, but in the english translation that is lost.
sorry for my english hahahaha, i hope that i was able to help
your english is fine :) that makes sense! i bought a copy of my fav bl thinking there would be a lot of furigana but boy was i wrong lol thanks for taking the time to respond!
no problem :)
I'm genuinely curious, I've recently purchased some bl mangas in Japan and I've noticed that only some of the kanji have furigana on it.. (which is such a drag since i can only read hiragana T___T) what's the reason for this?