If you loved Die verborgene Festung - Hidden Fortress, try Lorelei I-507 - Deutsche Wunderwaffe im Pazifik
Eine Brücke zwischen einem Film, den du schon gesehen hast, und einem, den kaum jemand kennt. Das teilen sie, und was der zweite macht, was der erste nicht macht.

Die verborgene Festung - Hidden Fortress

Lorelei I-507 - Deutsche Wunderwaffe im Pazifik
Was sie teilen
Both films are directed by Shinji Higuchi, and they both carry the slow burn mood tag, and they sit in Action / Drama territory. If that's the register that drew you to Die verborgene Festung - Hidden Fortress, the second film will land in a comparable space — through a different lens.
What Lorelei I-507 - Deutsche Wunderwaffe im Pazifik is
1945 Pacific, late summer. A constant ping. Last-hope sonarman Shinichi must distinguish enemy from ally as Japan teeters toward surrender. His submarine I-507 carries a mysterious young woman, Lorelei, who can detect approaching threats. A late entry in the post-Godzilla wave of mournful, FX-heavy war allegories.