The hand-drawn pastel beauty of Hiroyuki Okiura’s A Letter to Momo is a good tipoff to its maker’s emotional sensitivity. This animated world of mild blue seaside skies and fresh mossy woods is as safe an environment for an eleven-year-old girl to cope with grief as we could possibly ask for — even and especially when it gets permeated by mischievous supernatural forces. Momo relocates with her mother to a pastoral island after the death of her father; the letter in question is from him, but “Dear Momo” was as far as he got. So she carries it around with her, wondering what he wanted to say, and regretting the fight they had when last she saw him alive. Help is available from a trio of weirdo spirits — “Originally they were gods but had fallen into goblins,” as someone explains — and from Okiura, who respects both the complexity of grieving and the value of clowning without overplaying his hand on either front. So we have here a cartoon involving goblins that somehow manages to emphasize and appreciate the preciousness of human naturalism. Filmmakers of live-action fare, even that which ostensibly is aimed at adults, could learn a lot from its tact.