World Tour Mai Update - What are these key items Ive found?

So while doing Mais story in World tour Ive found 3 "ninja stones". They are key items called 1. Black Stone of the Frog, 2. Yellow Stone of the Bear 3. Red Stone of the Monkey. Their description says something about a Ninja that is interested in them. I looked nearly everywhere, Metro City, KOF, Nayshall. I cant find anything. Thanks for the help.