Siheyuan: I Was Supposed to Be a Mechanic, So Why Am I Catching Spies?

[Siheyuan courtyard setting + New plot + Counterespionage + Spy warfare + One heroine + Low on hostility] Zhang Tiansuo transmigrates to 1961, into Love in the Courtyard. He becomes a machine repairman and awakens a mission System: [Mission 1: Insult someone in the Beijing dialect, keeping it up for 30 seconds.] [Mission 2: Demonstrate the Silk-Winding Grappling Technique in public.] Meanwhile, undercurrents swirl through the courtyard and the steel mill, where enemy agents are secretly hiding! The Nine-Headed Eagle has entered the country in secret, and the Black Triangle organization is stirring up trouble once more! Zhang Tiansuo joins the Investigation Division, matching wits with the spies!