If mirin is available, substitute it for the 4 tablespoons of white wine and 1 tablespoon sugar.
Kikuna or shungika are edible chrysanthemum leaves that are traditionally used in sukiyaki and other Japanese soups and stews. I have substituted celery for 1 bunch of kikuna. Arugula is also a good substitution.
Feel free to use glass noodles in place of the udon.