Both with a lead that can see the ghost of the other lead, and both has a connection between the FL and ML with a mystery to be solved

Both main characters are introverts who prefer to be among robots than humans.
Both MLs fell in love with a robot.

Both are from the same universe/world
The main character in SBMS had a cameo in AR and it's special episode.
Both dramas are BL.

Both are BL
Both are in the same world
The main characters in Stay by my side appeared in Anti reset as themselves.

Both are special episodes from dramas in the same universe.
The main character in SBMS had a cameo appearance in AR special.

Both of them are adapted from the same BL novel, and basically the same story, just a remake.

1- Both are BL.
2- Both has boss / employee relationship .
3- Both are work romance.

-Psychopath male lead in disguise as an innocent man who teams up with a detective to solve a murder case and the twist that he is actually the killee was revealed later.
-In mouse he killed the detective brother while in trap he killed his partner.
-Both male leads tricked an innocent woman and killed someone precious to her.
-Both discussing psychopaths