When you think of 'Nanny', you probably will always want them as female in middle age because they are surely more experienced for handling children.   But.  

Bang Minah gets frustrated when her boyfriend disagrees to go with her to Japan. She leaves and finds herself alone in the streets of Tokyo and then meets a guy named Lee Taemin, who is purely handsome and mature, unlike her boyfriend. They undergo a series of drama when Minah goes back to Seoul and forgets all her memory about Taemin.