An 18-year-old youth, Xu Mengcheng, unexpectedly travels through the side door of an old residence and meets his 45-year-old self. His middle-aged self is burdened with debt, and still holds deep regrets of failing to save enough medical fees to save his grandfather and missing out on his love. After discovering the laws of time travel, the two decide to seize the era's opportunities in 1999, accumulating savings through the digital business. They run the shop steadily, resolve interpersonal conflicts, and work hand in hand with partners by their side to steadily strive ahead. While preparing for his grandfather's medical checkup fees, he bravely runs towards his youthful romance, rewriting a regretful life in their bidirectional efforts.