Asakiyume mita

Now that you mention it, I don't think I have read any other stories that have that particular combo. In Pamela Dean's Secret Country trilogy, the kids fix it so that no time passes while they're gone - but that's because they've read Narnia; and in any case they're only gone for a few weeks, IIRC.

In Delia Sherman's The Freedom Maze, the heroine is gone no time at all - but she grows a few inches while she's away, and that stays with her when she comes home. (Of course that's a somewhat different book, because she goes to the past rather than a fantasy land.)

Are Philip Pullman's His Dark Materials books portal fantasies? I suppose technically they are, although I don't usually think of them that way. The characters are banned from traveling between worlds eventually, but not because they've reached a certain age (although honestly I thought it was even more unfair than the ban in Narnia. I know the series is meant as an anti-Narnia reaction but I think it ends up repeating a lot of Narnia's mistakes and adding a few of its own).

I haven't read Lev Grossman's The Magicians, but it also is engaging specifically with Narnia, so I'm curious if it follows this template too.

And of course there's Oz or Wonderland, which are both different again, or something like Fog Magic where the fog serves as a portal of sorts - but the heroine is never gone more than an afternoon.