Irrelevant variables, also called control variables, refer to variables that affect the change of the dependent variable at the same time as the independent variable, but have nothing to do with the purpose of the research.
Liang Yi, an undercover police officer, can be said to be an irrelevant variable in this mission. Whether he is there or not, it has nothing to do with it.
An undercover police officer walking in a gray area falls in love with an upright policeman. His path is destined to be difficult.