If you loved Towa no Quon 1: The Ephemeral Petals, try Mobile Suit Gundam: The 08th MS Team - Miller's Report
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.

Towa no Quon 1: The Ephemeral Petals

Mobile Suit Gundam: The 08th MS Team - Miller's Report
What they share
Both films are directed by Umanosuke Iida, and they both carry the outsider, slow burn mood tags, and they sit in Action / Animation / Science Fiction territory. If that's the register that drew you to Towa no Quon 1: The Ephemeral Petals, the second film will land in a comparable space — through a different lens.
What Mobile Suit Gundam: The 08th MS Team - Miller's Report is
You investigate a mobile suit team in the jungles of Southeast Asia. Their recent skirmishes raise questions among Federation leaders. But the deeper you dig, the more tenuous the battle lines seem. Iida and Kanda's OVA episode offers a glimpse into the UC timeline's moral ambiguities.