Design student Gu Li and computer genius Du Jiangbai meet at a movie theater over a line of code for mechanical butterflies projected on the screen. A QR-code sesame cake drenched in milk tea, MATLAB analysis of how often their eyes crinkle with laughter, and heart-rate data logged at 5 km/h on a shared bike weave together a romance born from the collision of science and art. He preserves dumplings that burst while boiling in liquid nitrogen as "virus samples." She carves his outline into a mystery no code can decipher.
On a stormy night of betrayal, he swallows an anti-hangover pill and disguises his protection as milk tea-flavored devotion, then reopens a braised chicken shop in the ruins. When a sandstorm sweeps away the lab's data, an enlistment notice tears through the lipstick mark on a milk tea cup. A rusty military tag is engraved with "two years of grace," while her tears dissolve a confession that has been encrypted inside a sesame cake for three years.
After his discharge, the AI on their shared bike asks, "Would you like to renew your youth?" The buttons on her wedding dress are made from a bomb-disposal cutter forged into a wedding ring, and the molten center of their wedding cakes hides the frame rate of the movie where they first met. When a baby's cry activates the old code in a heart monitor, a mechanical butterfly reflects the answer, compiled over ten years, in his military goggles. Every algorithm error was a bug meticulously designed by love.
