Doom at Your Service

Both FLs are unlucky/having a hard time in life and become magically intertwined with the ML who is a lonely deity.

If you like love stories between a mortal woman with a terminal illness and an immortal being, both have this trope. Doom is more slice of life though.

Human in love with personification of death or destruction, hospital setting, melancholy feeling, focus on plants/growing things.

Different in tone but similar in characters and aesthetics. ML is a god like being, FL a human, and their relationship grows slowly. Also in the end, ML disappears, then returns as a human.

In both shows, the Male Lead is a Grim Reaper tasked with fetching souls. One of these souls they are supposed to fetch is the Female Leads'. But, in trying to accomplish their goal, they end up falling in love with her instead.

DAYS feels way more lighthearted than Black, though. While the former starts with some hilarious comedy at first, halfway through the series the crime element of the show turns the series dark (pun intended).

Here the main lead character of the drama is the doom itself. He soon falls in love with Tak Dong Kyung, who has just 100 days left to live. The male lead helps fl in both!!

Although different in tone (DAYS is darker), both are about a human FL who makes a deal with/becomes involved with the ML who is a personification of something (math vs. doom). Both MLs are cold and distant at first but become sweet when they fall in love. The FLs end up living at/attached to the ML's house which is sort of cold and barren, reflecting their life. Both dramas have a scene of wishing on meteors.

Both female leads find themselves in a difficult situation until they meet a man that will supposedly save them. They find themselves in situations where they end up faking their love (DAYS - so that he will die) (CLOY - So that she doesn't die or get caught as a South Korean). Through this, they both bicker quite a bit but eventually gain feelings for each other. Although they start to like each other, they both do not realise. The male leads have both made the promise to keep her safe but when she sacrifices herself, they become quite frustrated and realise they may have feelings.

The FL gets diagnosed with cancer and has given numerous days left to live. Because of this, she decides to quit her job and live her life to the fullest.

The story is similar to Doom at Your Service. You can feel a connection between both FL’s. The only crucial aspect that is different is that it doesn’t have fantasy.

In both dramas, the FL has a younger brother whom she cares for deeply. Both FLs have a brush with death.

Both are fantasy romance dramas where a supernatural being (gumiho / deity) becomes involved with a human, leading to a contract-style relationship that challenges fate and deals with life-and-death stakes

So, yes - there are similarities - unexplicable binge watching ability, good pace, no fillers.
Main resemblance - super human abilities - in Doom at your service - semi god, my lovely liar - FL with liars detection ability.

Even though at first glance they don't seem to have anything in common it's the atmosphere and the overall feel of the romance. In both shows the affections and bickerings between ML and FL are similarly adorable, feverish, loud, heartwarming, sad, joyous, melodramatic, hurtful, amusing, ...
They take you for an emotional ride and you become very invested in the relationships. Also in those of the supporting casts.

In both series, ML is a supernatural being that is kind of struggling with his existence. Both end up falling in love with FL, who is different from everyone else (in MMIC FL is basically cursed in love because of her past life; in DAYS FL has terminal cancer). And in both series ML disappears for a while but returns as a human.