Starting from the glass marbles in the starry sky lane at the age of six, Jiang Yanli and Lin Wanxing used butterflies as paper and formulas as oaths, and they guarded each other during the ten-year secret love - he used the convenience store hot cocoa to draw functions to hide his worries, and she used the income from illustrations to fill his debt gap; the "LX=∞" on the college entrance examination paper and the fingers clasped in the graduation photo were unspoken confessions.
When he was in a different place, he carved coordinates on the wooden sign, she founded the Butterfly Club, the struggle to give up studying under the pressure of reality, and the exchange of love letters from the iron gate made 1,200 kilometers the same frequency track of the heart. After marriage, the sea of butterfly lanterns reflects the first day of encounter, the B-ultrasound butterfly light spots illuminate new life, and the twin trees grow from wishing saplings to the time coordinates of three generations.
Under the tree in their old age, the moonlight reflected the leaves into the butterflies they drew when they were children. They finally understood that love is a twin tree planted by their own hands, with roots entwined and branches and leaves touching, growing forever in time.
