Both dramas are about high school students
Both dramas deal with high school suicide
both have vigilante fighting for justice

Both dramas has bullying in it
Both dramas about high school male lead fighting back
Both dramas are high school centered

Both dramas are school dramas
both dramas are dealing with dead students or dying male lead
both dramas has bullies and revenge

Both are from the same lost tomb drama series ,, same characters but different actors
not dark glasses ,, he's the same from tomb of the sea drama
both has action , adventure and male friendship

Both of the same series of lost tomb dramas and movies ,, with the same characters but different actors

similar plot in both dramas
similar objective of helping the bereaved people of dead loved ones
similar cute and funny sometimes leads

Both dramas deals with dead people wishes and how they can make them at peace
Both dramas give some kind of hope to the living people

Both are detective dramas
both have good partnership between a genius kid and a detective
Both have good criminal solving methods

Both have the same male lead
both are detective dramas
both have partnership
Both are unique perspective in solving crimes

it's the prequel of this drama as it tells a story of one family from the same era and the same composition of the story
they are technically connected plot wise
both have martial arts too in the same era

Both dramas have corrupt cops or seem to be corrupt and a lot of detective work involves drug gangs and very complicated relationships between the cops

Both dramas are drug related police dramas
who involves an undercover cop and a lot of thrilling events