If you loved Izo, try Ninja Kids!!!
A bridge between a film you've already seen and one most people haven't. Ninja Kids!!! has roughly 4.9× fewer votes than Izo — 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.
What they share
Both films are directed by Takashi Miike, and they sit in Action / Drama territory. If that's the register that drew you to Izo, the second film will land in a comparable space — through a different lens.
What Ninja Kids!!! is
Apparently ninjas start young. Rantaro is sent to a ninja training school by his parents. It all builds up to a chaotic mountain bell race.

