In the late Edo period, Japan faced an unprecedented crisis with the arrival of black ships from overseas. However, Japan drove away the black ships thanks to Onigami, giant robots that have existed in Japan since the ancient times. The country has remained in self-imposed seclusion from foreigners ever since. The story begins in this Japan that never experienced the Meiji Restoration.

In year 29 of the Divine Era, more than thirty years have passed since a mysterious monster from the heavens destroyed all of Japan except Shikoku. Young boys and girls, already unaware of the tragedy of that time, live in peace behind the wall that protect Shikoku. In such a time, there was a girl who was given the name "Yuuna" because of a special gesture she made at birth. Yuuna is an honorary name taken from Takashima Yuuna who perished in a fierce battle with the monsters about 30 years ago. Yuzuki Yuuna was one of those Yuunas, but contrary to her heroic name, she was a girl with no special powers. She learns that there is a girl in the same school with the same Yuuna name. Fuyou Lilienthal Yuuna — She says, "My dream is to go outside the wall and see the world for what it really is."

Winter Days is an amazing, visually stunning collaboration of the greatest animation masters in the world joining forces to create a visual Renku, a style of poetry specific to Japan whereby composers write a poem as a group, each poet creating a different verse. Winter Days is taken from the famous Japanese poet Basho's Seven Poetry Collection, the paradigm of the sho-fu style of haiku. Led by Kihachiro Kawamoto, Japan's greatest puppet animator, thirty-five animators from Japan, China, Belgium, Czech Republic, England, Netherlands, Canada, and Russia worked tirelessly to realize Winter Days, a thirty-six part Renku opening with delicious animation seamlessly flowing from one verse to the next before taking on the form of a documentary, illustrating behind the scenes interviews with the creators. Winter Days is a visual feast for animation and poetry lovers and those who embrace alternative and innovative approaches to the Renku art form.

If time did not allow ordinary things to be ordinary. How would you have lived? It is the Bakumatsu and early Meiji Period. Akizuki Keiichirou and Kusaka Touma stand of opposite sides of the political scale of the time but still, something as fragile as the shell of a cicada binds these two men together in a tragic and cruel fate. A story of friendship, love and seperation as well as reunion and sacrifice.