The joint
木漏れ日 is three morphemes and one perception: the sun, leaking, through trees. It is a noun. You can say there was komorebi on the path the way you can say there was fog. English can say “sunlight filtering through the leaves,” and the picture is the same picture. What English does not have is the single established item.
That is the whole break, and it is a small one. The “untranslatable Japanese word” industry likes this noun because the picture is pretty. Prettiness is not a linguistic category. The linguistic category is packaging. A scene has been lexicalized. A language that has not lexicalized it is not blind. It is differently indexed.
German, French, Spanish, and Chinese glosses on this plate all succeed as descriptions and all fail as headwords. Dots of light, god rays, dappled shade: English has neighboring phrases, none of them this compound. Using them is good writing. Calling them equivalents is the overclaim.
Why this break matters to a reader
A reader of a translation that says “the light through the leaves” has seen the thing. A reader of a translation that says “komorebi” and stops has been given a password. The password matters only if the noun-ness matters: that Japanese can point at this light as a kind, the way a field guide points. In a poem, the noun can be the point. In a caption, the description is enough. The map’s job is to say which of those you were denied, and the answer is the headword, not the sight.