If you loved Hotarubi no Mori e, try Natsume's Book of Friends the Movie: Ephemeral Bond
A bridge between a film you've already seen and one most people haven't. Natsume's Book of Friends the Movie: Ephemeral Bond has roughly 37.8× fewer votes than Hotarubi no Mori e — it's a deeper cut, not a mainstream recommendation. Here's what they share, and what the second one does that the first one doesn't.

Hotarubi no Mori e

Natsume's Book of Friends the Movie: Ephemeral Bond
What they share
Both films are directed by Takahiro Omori, and they both carry the bittersweet, foreign gem, tender mood tags, and they sit in Animation / Fantasy territory. If that's the register that drew you to Hotarubi no Mori e, the second film will land in a comparable space — through a different lens.
What Natsume's Book of Friends the Movie: Ephemeral Bond is
Spirited Away meets My Neighbor Totoro. Natsume reunites with an old classmate and meets a woman connected to a Yokai. It delivers gentle fantasy.