The Master's Sun

Both the series consist of a character who can interact with ghosts. And the ability is used to solve crimes in the society with the help from the ghosts.

Both main leads led cold life's and became close to awesome female leads with an ability to see dead people.

Raak boon female lead is very strong willed, feisty and doesn't want anyone's pity.

—Paranormal theme for the win.
—The roles are switched but one of the main characters needs the other for their "survival" and takes up a job to be close to them.
— slow burn romance.
—tragic past events shaped their present situations

Although the plot is totally different..but in both the stories romance between the main leads start with the need of being with each other rather than love. And also, the FL has a crush on the SML at the beginning..;p

They both have a ghost seeing FL. The ML have something about them that make the ghosts disappear which encourages the FL to be around them more.

Both dramas include Ghosts
It also includes the Female leads being able to see and to communicate with Ghosts.

the leads in both can see ghosts and ghosts follow them around to relieve their grievances.

it's not excatly the same plot but in both series the female lead is able to see ghosts.
if you liked Ghost friends I highly recommend watching the master's sun

Native Title: ??? ??
Also Known As: The Sun of My Master , The Sun Of The Lord , Master's Sun , Joogoonui Taeyang , Jugunui Taeyang
Screenwriter: Hong Jung Eun, Hong Mi Ran
Director: Jin Hyeok
Genres: Horror, Comedy, Romance, Supernatural
Tags: Ghost, Eccentric Female Lead, Ghost-seeing Female Lead, Rich Male Lead, Clingy Female Lead, Successful Male Lead, Trauma, Secondary Couple, Eccentric Male Lead, Hidden Identity

If you want more thriller (but not ghosts, unfortunately) Healer has it too...

Also balanced with bickering romance... Just check it out... Highly recommended!!

Both have quirky bosses falling in love with their subordinates. Fox's Summer is a fluffier and funny series, with a sassy and feisty lead girl. No paranormal or fantasy storyline in FS.

Both has a supernatural element to it. In Goblin, Eun Tak can call him by blowing a candle. In Master's Sun, Tae Gong Shil can avoid ghosts by touching him.

While very different in plot, both dramas have a ghost-seeing FL and a "unique" ML (he can chase her ghosts away vs. he can help her because he isn't human). Both have horror elements and a slow-burn romance.

They both have ghosts with unresolved problems stopping them going onto the afterlife which are dealt with by the main characters.

Both female heroine can see ghosts
Although Black is truly a serious crime-drama-fantasy, The Master's Sun is more light-hearted, romantic drama
Both dramas are worth watching!!