I'll take you to see Shiro. That's a promise!" Jin, a cat, promised Mugi, who was saddened by the loss of her beloved dog Shiro. Jin, who loves Mugi, heard an anecdote about the "Rainbow Bridge" from his owner, Aki, and decided to take Mugi to see Shiro at the foot of the rainbow! Will Jin be able to save Mugi from his grief? Jin invites the pigeons and squirrels in the neighborhood to join him on his grand mission!