I do not know the legal status of his work. However, the term "art assets" implies, to me, particular works. In that sense, he is not reusing "art assets" - the

I do not know the legal status of his work. However, the term "art assets" implies, to me, particular works. In that sense, he is not reusing "art assets" - these works are his own, but obviously inspired by work that Nintendo owns the copyright to. I am unsure what legal status fan art in general occupies: it's original art, but obviously derived from something someone else owns. Trademark may be a clearer case: he's clearly reusing trademarked terms in a context that could cause someone to believe they are from the trademark owners. Anyway, I hope he's allowed to continue making and selling them. They're amazing, and should exist.