Male lead left behind the clues because second male lead has the curse but work different way if second male lead truly love someone they get injured , the way he said that i violated all the rules that he knows he fell in love with second female lead thats why he try to keep the distance to protect her , male lead left those clues behind that second male lead slove the case and let go of his past guilt also giving the case file to female lead mean male lead waiting that island until she come to male lead because the only way to cure the curse is finding the true love , so female lead should truly love male lead , and second female lead also truly love second male lead that is only way to escape from loneliness ,
This just a idea