Suddenly Seventeen

Liang Xia is a gifted painter who gave up a bright career to be the ideal girlfriend, while Mao prioritizes his design work. They have been together for nearly a decade and live in Beijing. Liang waits for a marriage proposal that never comes as they drift apart, setting the emotional stage for the film.

One morning Liang sees a flashy infomercial claiming the chocolates can restore youthful energy. She impulsively orders a box, hoping to shake up her stagnant life. The purchase introduces a magical device that will inexorably alter her fate.

Bai Xiaoning schemes to force a public marriage proposal at her wedding with Liang as the surprise center of attention. The plan relies on crowd reaction and timing, but it quickly begins to unravel. The effort pulls both Liang and Bai into trouble and exposes underlying tensions.

Mao reacts to the failed scheme with threats to end the relationship, leaving Liang devastated. She confronts the sense that her hope for romance is slipping away. This emotional blow sets the stage for her impulsive chocolate consumption.

Liang swallows another chocolate and wakes up transformed into her younger self, a 17-year-old, while somehow experiencing time ahead in her life. She is effectively 11 years ahead in her future, creating a disorienting split in identity. The change triggers a cascade of identity conflicts and new possibilities.

The 17-year-old Little Liang begins to explore a carefree life under Bai's friendship, while the older Big Liang tries to navigate her grown life and understand the new artistic possibilities. The two halves communicate through subtle glimpses and shared memories, drawing strength from their unique bond. Bai's reactions to the younger Liang mix awe with protective concern.

Little Liang meets a striking young man named Yan Yan while sketching him on a subway platform. A spark forms as drawings become a connection across time, but the spell wears off soon after. The encounter leaves Yan with a drawing and Liang with tangled feelings.

Big Liang and Little Liang begin to communicate through video messages and voice notes stored in their devices, sharing ideas and plans. The exchange exposes their conflicting priorities: Big Liang wants to prove her worth, while Little Liang yearns for romance and freedom. The messages keep both Liangs tethered to each other despite the time split.

Big Liang reluctantly enlists Little Liang to help with designs for Mao's agency, and her youthful spark shines through in Little Liang's sketches. A major contract is awarded, signaling a professional comeback for Liang. Mao is impressed, recognizing a renewed artistic fire in their work.

Mao confesses to Xiao Yu that he doubts the couple will stay together in the long term. Overhearing this, Big Liang sinks into despair and retreats home, where she consumes another chocolate. The moment exposes the fragility of their bond and the limits of the chocolate's power.

The chocolates' origin factory is destroyed in a meteor accident, leaving only a handful of doses. Big Liang and Little Liang realize their time together is limited and decide to push their collaboration further. This turn raises the stakes for both of them as their shared art becomes their lifeline.

Big Liang leaves a farewell message for Little Liang and consumes the last chocolate that can sustain their presence. Little Liang continues to influence Liang's life while facing an uncertain future. The act marks the end of a planned separation and a fragile reconciliation through art.

Desperation drives Little Liang to take nine chocolates at once to stay longer, and she collapses on a train platform. She is rushed to a hospital, where Liang's psyche merges the two halves for the first time in a mental confrontation. Big Liang consoles the younger self and the two halves begin to heal, allowing her to return to life.

Time passes and a digital billboard in a new city glows with Liang's design, signaling a lasting artistic legacy. Mao frantically runs through the city streets naked, carrying a sign asking Liang to take him back. The ending keeps the door open for reconciliation and the power of art and memory to move through time.