They are connected. same characters and story. the special comes out in 2015 so you understand the story better if you watch it in order. the story does make sense if you don`t

investigation on what actually happened in the past. taking down criminals from the crime that they have done. getting revenge for themselves and the other victims that could be connected to the investigation.

investigation of what happened in the past. taking down bad gay that either hurt or scam people and getting revenge from the victims of those crimes/ scams

just you, Apart from it not being a BL the description is similar. there is a new CEO that comes in and helps a company he puts up a notice for no office romance but it turns out he is just hurting from a past relationship. the employees try to help him overcome his pain to get the new rule of no office romance abolished

both about the clothes industry in ancient times. the male and female leads have great chemistry . the male lead in ni chang knows martial arts but the male lead in overlord doen`t.

both male leads are princes and are good at martial arts. both female leads families are falsely accused and killed. both investigate the crime and find the real culprit

both about school but one is set in high school and the other is set in college. about the lives of the players within and without the team

both about basketball team players and their lives. the troubles and difficulties they have juggling school family life and basketball.

it's about healing and death and mystery. more mystery in its okay to not be okay. one of the main characters in both are disabled mentally and need help with things they don't understand.

about human experimentation. also about the police and investigation. the human experiment gets discovered during an investigation. a lot of the characters die randomly and unexpectedly. a lot of twists and turns and the bad guy isn`t who you expect.

there are both about an amusement park. the male lead wants to tear it down and the female lead wants to save it. slowly but surely the cold-hearted businessman (male lead) warms up to the cheerful but naive girl (female lead) and eventually they fall in love.

both have assassin that wants to let go of the past and redeem themselves. although word of honor is more fantasy-based one of the main characters in both have similar backgrounds and get dragged into a conspiracy to do with the past. even though they don't want anything to do with it at first they fight to protect their new found life.