If you loved Dragon Ball Z: Summer Vacation Special, try Saint Seiya: Evil Goddess Eris
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

Dragon Ball Z: Summer Vacation Special
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Saint Seiya: Evil Goddess Eris
What they share
Both films are directed by Kouzou Morishita, and they both carry the playful mood tag, and they sit in Animation territory. If that's the register that drew you to Dragon Ball Z: Summer Vacation Special, the second film will land in a comparable space — through a different lens.
playful
What Saint Seiya: Evil Goddess Eris is
You train at Sanctuary to become a Bronze Saint, but your friend is gravely wounded in a bizarre attack. Then ghostly warriors appear, serving the goddess Eris. Morishita’s direction emphasizes the uncanny character designs. The film suggests shonen anime's formulaic pleasures.