First of all i want to say a small disclaimer lol I do believe in past lives so the concept of this drama was close to the reality i imagine to be. I will try to be as objective as possible but we are all people and have our preferences so all the reviews will always be subjective based on our own likes and dislikes. So if i liked this or disliked this doesn't mean you will too :) I had a drama slump and took a break from dramas for many months :) (i thought this is important). I binged (slowly) this drama in 4 days.

Overall i liked this drama :) and recommend it to the ones who like fantasy genre. Just try not to expect much. Expectations might ruin it a lot. Also try to go passed the first 3 eps. :) Oh and i think this is more suited for binge watching rather than ongoing. Shorter review at the end.

Story:
If i were to give different rating to story/plot and the concept i would give the concept 10 and the plot 7. The concept is great! past lives, reincarnations, and how people connected in the past lives will always be connected again, that is karma, and until it is fulfilled even enemies can become relatives. (i do think this is what happens in rl too, so that might have kinda influenced the way i saw this drama) I do like that this also is taking a big span, so not just one past life, but many. On the other hand the plot that was based on this concept was sometimes inconsistent. By inconsistency i mean they waited a very very very long time to reveal us the real truth but they left out some of the big questions. I would have liked to know the answers to some but as the drama didn't give any answers i just theories my own. This is another thing, Theorizing of who is who and what is what was fun. Most of the stuff i was thinking turned out to be true (which i don't really like) but it's okay xD The real big big truth might have been underwhelming because of how "simple" it was, It was kinda the misunderstanding type of thing, i did wish for a bigger and more impactful thing, but this truth was relatable and kinda what happens all the time in our lives every second. The envy, rage, miserableness, being left behind, loving someone, wishing power, revenge... all that is something we have seen countless times, but it is what is always moving this world. Also as everything was revealed at the very end it might have felt rushed for many people. I binged this so that didn't feel rushed, it felt a little bit dragged even.
I didn't like how bloody it was. especially the start! i was going to drop it after the first ep, and then after the second too. But then it got interesting for me (and my mom). I have seen people for whom it was the other way around so i guess it is the matter of preference. The first two eps were about the past, and there was lots of blood. Then there was more blood near the end.
I liked the incorporation of the folklore demons. Though it felt like huge anime arcs squished into one ep each. The way they were introducing the demons/monsters was really anime like, it made me remember all those hyakunin ikki and stuff. Would have been better to elaborate more on them, but it might have become more draggy for a drama. If so they could have squished it more and removed some of the demons making less episodes, as they were not the main plot.
The concept of bulgasal was also nice (something like an immortal being) but they kinda merged it with vampires/zombies. which is okay i guess as there seem to be a zombie craze.
I didn't look at the actors list so i was surprised when they revealed the villain.
More weird things were when the house was suddenly a super lived in house, hurt person suddenly appearing lying outside when he was in car just now, how did he fly there remains a mystery! and some other small inconsistencies.
revenge all around, makes me remember naruto as that was the one of the best explanations of the endless revenge circle i have seen lol but still it was okay. Also the sacrifice talks also were okay for me, as that was what i thought would have been right to do too.
I think they could have dome much more and explained more in the story. But it was still okay and good for me as i fully theorized the rest. I really liked some parts of the real truth as it was indeed resonating with my own beliefs about family and enemies and karma. I would have liked if they elaborated more on the villain and the brother (i won't tell what brother) but still it was alright! so thank you for the story!
Characters/Acting:
There were few characters but they were all interesting. The ml was a bit plain for me, though the rough look, the size and everything suited the role i guess. This is purely personal preference and doesn't mean that the actor didn't do a great job. I did like the fl though. I only remembered that actress from iteawon class and couldn't imagine her as main, but i was pleasantly surprised! Min Sang Un for us is a start of everything and our hatred goes to her from the first ep. The second ep focuses more on her reincarnation "asking for sympathy towards the villain" which was really weird! Later we see her grown up, being a lovely bubbly girl, which made me feel proud of her as it is extremely hard to maintain a good personality in such circumstances. I love that kind of characters. But at the corner of our minds we keep thinking that she is bad, we mustn't like her, just like some of the side characters think. But as the story progresses we learn more and more, slowly we start to see her in different light. She was strong despite everything and followed her beliefs no matter what to protect her family.
the ml on the other hand is consistent but then slowly also changes near the end.
The villain was amazing. Acting was top notch, i remembered the gap dong days! Anyway we were slowly starting to feel sympathy for him. It was very well done, but at the end his story was a little bit underwhelming, so don't expect anything grand. It was something i would come up with if i was a writer, but i would wish something greater from a professional. But! at the same time it was very normal, i mean something like that happiness all the time and the feelings he got and the acts he did happened a lot back then. Which is just simply sad.
The side characters like mr. detective, heeseok aunty, doyoon, and shiho each of them had their story and it was interesting to see all the connections in the end. I loved it. The actors also did a great job! Shi ho is the best i love her and she is gorgeous! Though I was really frustrated at them a lot because as usual, like in any drama the side characters get always in the way and get used. So if you are weak please, just please, stay at home and don't try to act! let the strong people do stuff! that is called helping!
Addressing romance: if you plan to see romance here it's better not, but if you plan not to feel any romance here you better not as well lol. I knew there will be romance, because how can they do it without romance? XD they just neeeed it! (sarcasm) but if in all honesty, was it forced? Anyone will fall in love with a person who saves them, especially if they didn't talk with anyone before, and no one saved them before. I would too. But the love that was there did feel forced sometimes when it was too strong, though at the same time after everything was revealed i started understand why. The past connections have their influence, and the connection we see at the first two eps is like a drop in the ocean, and not the whole truth. But the overall romance is mostly around, taking care of wounds, a piggyback ride, couple of looks, and being sad of the thought of the other one dying. That's all, and i'm happy with it.

Music:
what can i say! music was great! <3 i loved some of the songs!

Rewatch value:
I never rewatch dramas so there is a random number there.

Overall!!
i liked it a lot :) I had a break from dramas for many months so maybe it played a huge role but i really enjoyed this one with my mom, very interesting, was something to look forward to everyday! :)

Short review:
Liked:
-her hair! <3 xD
-concept of past lives and how it was handled (for me it was much better than other dramas who did this before, if you know anything better let me know, I'd like to see more :D )
-all the connections
-monsters (nice idea but maybe not necessary here, idk)
-the fast pace

Disliked:
-a lot of driving around
-house suddenly filled with flower pots lol
-suddenly flying out of the car (idk how)
-twins (would go to likes if explained)
-ml
-too much blood!!! why >< they try to copy western shows but i hope they don't
-monsters( nice idea but maybe not necessary here, idk)
-weaklings not staying out of the way but trying to help.
-unanswered questions! too many lol i didn't think of them when i just finished as those questions were kinda active at the very start but i forgot about them later. Now when i look back, there were too many, and all left unanswered. But it's okay as the after taste was still good! i mean bittersweet.
-brother at the very start, was important as it's the start but this was left out completely.