If you loved 20th Century Boys 2: The Last Hope, try 20th Century Boys 3: Redemption
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.
You already loved

20th Century Boys 2: The Last Hope
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20th Century Boys 3: Redemption
What they share
Both films are directed by Yukihiko Tsutsumi, and they sit in Adventure / Mystery / Science Fiction territory. If that's the register that drew you to 20th Century Boys 2: The Last Hope, the second film will land in a comparable space — through a different lens.
What 20th Century Boys 3: Redemption is
Osaka, 2017. A single memory of a childhood flag. Kanna leads a ragtag band of rebels against the Friend regime, while Kenji's song inspires hope among the oppressed. One choice remains. Tsutsumi closes out his trilogy with pulp momentum.