Why can't I add the japanese version of Idol when I have the english version

It may because on Apple Music they both have the same name and artist so it thinks they're the same song. they need to change the japanese versions name back to japanese to fix it. all we can do is try to bring this to apple's attention. this issue isn't on other music apps, its apple music's problem.

actually, after playing around a bit i managed to get it to work

i had to

1. remove both versions from my library
2. go to settings and turn off the feature to automatically add songs to your library when you add them to a playlist (if on)
3. add one version to library by song and the other from it's album.

i then added both to a playlist (via method of adding to library) and it worked. both were different.

(be sure to check album cover and lyric language to confirm. english album cover says 'idol' & japanese album cover says 'アイドル')

it glitches and thinks both versions are different songs in the same album (for me it's the japanese album)

(you may be able to do it if you add both to your library via album but i'm not gonna risk messing things up to confirm, sorry)

as it's a glitch, it may not work.

(if any apple staff see this, don't try to patch the glitch until you fix the problem, and let the japanese version be available in places besides japan)

I’ve had the same issue in reverse. I had the Japanese version and wanted to add the English version. Every time I add it to my library, it immediately removes it. If I add it to a playlist directly from the store, it adds the Japanese version again to the playlist even when I’m selecting the English version.