Doom at Your Service

Both are fantasy themed dramas about male lead being creature from different world - god and grim reaper and human female lead.

I was really shocked how similar I found those two titles.
Not by story, but by aesthetics.
I thought, I was convinced, that those titles are connected by the same director and yet I was wrong which is amazing.
Still I think that JBL has better acting and music than DAYS (hehehe I just did ‘days’ while typing the shortage of the title, lol).
Yeah, but the vibe in DAYS is like mix of JBL and Goblin.

Yamihara Kokoro and Asada Toramatsu live in a town that is quite peaceful, until a serial murder case happened where the bodies all had their blood drained out. Five years have passed but the case remains unsolved. Meanwhile, Kokoro and Toramatsu have been in a relationship for a year, but are unable to get married as they are keeping a serious secret from each other. Kokoro is actually a vampire. However, she does not attack humans and live modestly. Toramatsu is a popular resident in the town and is trusted by many. After getting a divorce, Toramatsu got drunk and went back to his old house, where he met Kokoro, the current occupant. As the two continue to keep their secrets hidden, a horrific murder occurs once again in the town.

they don't have a lot of similarities but both are TvN dramas and both female leads have brain tumors and they are going to die
both are romantic comedies
both are on Netflix

Both of these shows have the FL as she is about to die being greeted by a grim reaper of sorts to help her during her final days, and they slowly fall in love. Both shows have beautiful colour palettes and heart wrenching emotional scenes, and are mainly character driven. I highly recommend both shows.

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.

After receiving a terminal diagnosis, a devoted husband discovers his wife’s affair. With little time left and his son’s future at stake, he embarks on a relentless quest for revenge that will change their family forever.

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!!

One day, Morikawa Natsumi suffers an accident. Unable to be seen or speak to anyone, she becomes a ghost wandering the streets. She's shocked when she finally manages to make eye contact with a young man -- Ichijo Ryouei, a handsome heir and fellow ghost also drifting through the city. This is the prequel to the "Memory Arc" and "Love Arc", depicting the irreplaceable days Natsumi and Ryouei spent together after their first fateful meeting in the afterlife, along with the relentless pursuit of the Grim Reaper chasing them. This is an original story not found in the webtoon.

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.