That name is temporarily invalid according to the website / metadata service right now, because it’s using ultra-strict rules that mark too many names as invalid.
Devs are working on normalization updates for the UI and metadata service ENS Name Normalization - #90 by raffy
The code is not final, but you can use this live demo tool to get an idea of what will be valid or invalid ENS Resolver
Japanese names like that, including ones with the elongation character, should be valid:
That name should become valid again once the normalization changes are finished.