大晦日、実家に帰ると母がいなかった。
息子の泉は、夜の公園でブランコに乗った母・百合子を見つける。
それは母が息子を忘れていく日々の始まりだった。

認知症と診断され、徐々に息子を忘れていく母を介護しながら、泉は母との思い出を蘇らせていく。
ふたりで生きてきた親子には、どうしても忘れることができない出来事があった。
母の記憶が失われていくなかで、泉は思い出す。
あのとき「一度、母を失った」ことを。
泉は封印されていた過去に、手をのばすーー。

現代において、失われていくもの、残り続けるものとは何か。
すべてを忘れていく母が、思い出させてくれたこととは何か。

On New Year’s Eve, when he returned home to his parents’ house, his mother was gone.
Her son Izumi finds his mother Yuriko on a swing at the park at night.
That was the beginning of the days when his mother began to forget her son.

Izumi, while caring for his mother, who is diagnosed with dementia and gradually forgets his son, begins to revive memories of his mother.
The two had lived together for a long time, but there was one event that they could not forget.
As her mother’s memory fades, Izumi remembers.
Izumi remembers that she lost her mother once.
Izumi reaches into her sealed past.

What is lost and what remains in the present age?
What did her mother, who was forgetting everything, remind her of?