Even though it has a different story background, Marry My Dead Body has the same story concept as 7 Days Before Valentine. Where the main character wants to return to his old partner. In MMDB: Mao Bang Yu wanted to visit his old boyfirend, with the help of Wu Ming Han, but unfortunately something unexpected happened. Even though they don't focus on that kind of thing, both are supernatural and the main character communicates with astral beings (spirits) who guide or at least provide good experiences for the other main characters.
They're both dialogue heavy and watch more like plays than television, they both grapple with themes of grief and isolation, they're both stories about young queer men without really being genre-complacent BLs, they both rely heavily on visual symbolism, and they both end on cathartic new beginnings.
The male leads are both being surrounded by spirits. But also their differences make both series unique. "7 Days Before Valentine" surrounds Sunshine who needs to understand that the world doesn't revolve around him rather to understand who we are and what our purpose is, while at the same time knowing others and understanding them as well. In "The Whisperer", the male lead Khun has always been told that he's crazy and only does "bad things". However, he won't seek revenge towards those to have lied to him, rather show them what "crazy" really is.