I’ve asked a few native Japanese speaker friends of mine, and one has never heard of “yuujin,” while the others have heard of the word but have never used it. I thought “tomodachi” was more widely used, no matter the context of conversation. Any reason why WK would teach a word not widely used? I even did some Googling and my friends’ testimonies hold up in comparison with the articles I’ve read.
Not trying to be harsh here, but there is zero chance a native speaker hasn’t heard of the word 友人. It’s more formal/literary than 友達, which is why using it in conversation would not be the best idea, but it’s a perfectly common word.
It’s in the top 1400 most frequent words on jpdb, which tracks frequency in works of fiction. It’s used in 85% of novels tracked there.
It’s something they would learn to read and write in 2nd grade.
He’s been pretty solid with other words and context I’ve asked him about. Again, his second language is English and he’s not fluent, so he probably did not mean “never.” But thanks anyway for your insight. I’ll take it with a grain of salt