Modern youth Su Yuan accidentally uncovers an old writing brush. At the end of the brush shaft is a crack that, when moistened with water, can form a crossing water curtain on the desktop, connecting modern times with the State of Qin in 237 BC. The three-year-old eldest young master of Qin, Fu Su, crawled out from this water curtain. From then on, Su Yuan's modern living room and the side hall of Xianyang Palace were quietly connected by a writing brush that leaks water, opening up their encounter spanning two thousand years. Su Yuan teaches Fu Su to drink yogurt and ride a balance bike, and Fu Su also brings the warmth of modern times back to the State of Qin, letting Ying Zheng taste steamed buns and instant noodles, whereby the trajectory of history is also quietly changing.