As Splinter's owner, Yoshi was the greatest shadow warrior of the Foot Clan in Japan, and trained Splinter in the art of ninjutsu by allowing the rat to copy his katas from inside his cage.
In the 1987 cartoon, Yoshi (voiced by Peter Reneday) was a Foot Clan shidoshi trained under the wise master Pasang back in Japan, but exiled himself to New York City after being framed by Oroku Saki for the attempted murder of a visiting sensei.