Remember a movie where a squirrel/chipmunk from the city decides to leave and gets chased by a Fox eventually?

It's a cartoon movie from the 90s or late 80s. Done in japanese
animation style. I've been trying to find this for a while as I
remember loving it when I was a little kid. I can't really remember
much from it, but the chipmunk/squirrel decides to leave the city and
go back to the forest for some reason. Eventually there's a scene
where he gets chased by this intense Fox. I can't remember how it ends
either.