Way Back Love

Way Back Love is a Korean Drama, 24-year-old girl, Jung Hui Wan, who's totally checked out of life. Like, she's basically living as a hermit. Then, out of nowhere, her childhood best friend and crush, Kim Ram U, shows up. Thing is, he's been dead for six years! Turns out, he's a grim reaper now.
Back in the day, they were super close and totally had a thing for each other, but neither of them ever said anything. Then, boom, he dies in an accident. Now, he's telling her she's got a week to live. He says if she wants a peaceful exit, she just needs to say his name three times.
Hui Wan, who's super lonely, is like, "Nope, not losing him again!" So, she refuses. Ram U, being a good friend (even as a reaper), gets her to make a bucket list of stuff she wants to do before she kicks the bucket, and they go on adventures together to tick everything off.