Midlife Crisis: Can We Be Friends? summary:

As a result of the successful crackdown on the gangsters, "Jitae" is in crisis due to "Taehun". Along with his collection of money, all his s** partners are caught by the prosecution.. Jitae, who is left alone, is driven by a desire for revenge and sends numerous letters containing sexual harassment to Taehun, who is suffering from work disruptions. Eventually, in a fit of rage, Taehun confirms the sender of the letters and discovers that it is his high school classmate, "Lee Jitae"?!+