Synopsis: The story begins with an engagement ring that was left in the MRT carriage. It should have been a romantic day for Yi Zhi to propose to Lisa, but the ring was lost by Yi Zhi, the marriage proposal may be disrupted, and in the process of retrieving the ring, they began to re-examine what love meant to each other. On the other hand, this ring also began to wander in this city. With the rapid transit of the MRT, after passing from station to station, it also struck a love story after another. This ring, like “love” in your heart and my heart, is constantly flowing in the city.