This was an idea and an unfinished script of Sion Sono, which was never realized. Tak Sakaguchi took the project over and it morphed into Crazy Samurai Musashi (2020).
In Why Don't You Play in Hell? (2013), Sion Sono's film made around the same time as the work on Kenkichi, the main characters who are amateur filmmakers watch a trailer they have made for their own film called "The Blood of Wolves", though they haven't actually made the movie itself yet, and never do. That was the working title of this movie Kenkichi, a film that was also never made.