What's nice about this is that the parents are fully aware of the falseness of the situation. Their child is gone, but welcome a stand in with the tanuki. The tanuki is in need of a home.
I don't necessarily see this becoming "tragic" as the potential rug pull of the falsity is handled immediately. However, I do believe it will come to a point where the parents are ready to let go entirely and either let the tanuki go or treat the tanuki as a new part of the family, free of Yuzu entirely.