OK, yeah. Even still, looking into Japanese copyright law (as an outsider with little understanding), it doesn't seem like there's anything that would protect against this, which makes sense because that'd be crazy. This is a totally new work that happens to operate on existing work. It doesn't use anything created by Nintendo. It should not be an issue.

If you can point to something that actually says this would be protected against, go for it. I highly doubt there is such a thing though. It'd make something like a printer with a scanner potentially illegal because it operates on someone else's works to produce an output.