Remember the time Sangwoo and Bum went on the hiking trip to despose of that girl's body and Bum acidentaly steped on his dad's grave...and also in the ca rwhen Bum asked Sangwoo if he ever went there before, Sangwoo replied that he did, the mom was driving and the dad was "sleeping" in the back....It might be that the mother killed him and made Sangwoo go help to get rid of the body
Remember the time Sangwoo and Bum went on the hiking trip to despose of that girl's body and Bum acidentaly steped on his dad's grave...and also in the ca rwhen Bum asked Sangwoo if he ever went there before, Sangwoo replied that he did, the mom was driving and the dad was "sleeping" in the back....It might be that the mother killed him and made Sangwoo go help to get rid of the body