RandomUsagi

At the moment 2 male characters are still suspects considering the identity of the serial-killer. Detective is obviously not it. I wrote a detailed analysis of all the suspects in another recent comment. I'd suggest reading that too.
It's either Sun Ho (partner of detective) or the Webcomic assistant of Ga Hyun.

The story is lowkey hinting at Sun Ho through specific scenes of him spying on the detective but this is just him being worried in my opinion. I think the writers want us to suspect Sun Ho so it's easier to hide the real culprit. He doesn't have a motive at this point and while it would be ironic if it was him it's unlikely.

The only one with a clear motive at this point is the webcomic assistant of Ga Hyun. Some people suspect the detective because of his love of the webcomic ''Hidden Killer'' but forget about the fanboy that cares the most about the webcomic. He could easily stalk Ga Hyun to find out her recent contacts. If he properly spied on her he may even be aware of the resetters. By killing he either shows he wants to act out a real version of the webcomic or he wants to inspire Ga Hyun. The nerdy look is to make him look more innocent and he acts a bit dumb but we really don't know anything about this guy besides his work.

Let's go back to the mysterious serial killer figure himself. A male character who is capable of hiding his tracks. His room is empty besides the glass cases with mementos and the empty picture-frames. There's also a projector creating an unknown image in the room and a lamp. Most importantly though, a black bag is hanging on the wall in the middle of the camera shot. By rewatching episodes I found out which character owns the black bag, it's always with the webcomic assistant. If he is the killer Ga Hyun will likely see some suspicious stuff in the documents he gave her.

If this is true than the true culprit would've been hinted at since episode 4. Anyway, I never would've caught onto it if it wasn't for the writers trying to make the Detective and Sun Ho into suspects this last episode. I'm very protective of those characters and their bond. This still leaves questions and who knows I may be wrong of course but we'll see.

The saved reset-participants were selected for currently unknown reasons but they are basically all experiments in avoiding death/fate. After saving them Lee Shin called them all up and did a group reset without warning them that they would likely die in the new timeline.
Now what do we basically have in this newest timeline?
The dying group-resetters, a serial killer, Lee Shin's daughter and Lee Shin as an onlooker.
The group-resetters basically cause drama within their own group but that's it. Lee Shin and the serial killer are the real important ones. Especially since even Lee Shin does not know the serial killers identity.
The important questions right now are:
-Who is the serial killer of the resetters? I personally think I identified him already.
-How is Lee Shin's daughter involved in the reset (likely the original reset-motive)?
-Who is the mysterious professor that Lee Shin contacts?
-Who is selected to die next? (Coffeeshop owner/Gamer-bro)
-Why was the reset-group specifically selected? (Why did Lee Shin choose them?)

Definitely! I'm glad I started the series while it was airing so I got to think of possible explanations for weird events/suspicious people with other people without having to worry about spoilers myself. This series is best enjoyed when you just try to figure the mystery out yourself/with people watching at the same time.

I finally found my definitive serial killer suspect after hours of research (rewatching episodes). Purely fueled by intent to protect the bond between Sun Ho and the detective. I'll list all leftover suspects.

Detective: Sure the end-scene was shocking but it was misleading. In my eyes the detective is innocent and most people likely agree with that since he has different shoes and he's not the type of person to kill in order to get what he wants. Sure he is a fanboy of ''Hidden Killer'' but he could've started murdering people in his original timeline instead of wasting all this effort to travel to the past. He just didn't want the police to immediately detain him as a suspect since there was critical reset-information at the dead gangsters house.The fact that Ga Hyun still suspects him is crazy to me but I get that there's paranoia when you likely have less than a year to live.

Gamer-bro: He is just as confused and desperate as the other characters. In the preview for the next episode it even shows him being scared by someone. He is used to having others do violent acts for him like bullying, not used to being violent himself.

Sun Ho (partner of detective): He has the knowledge to pull of this murder-stuff and it would fit with the whole speech from Lee Shin that the detective ''made a mistake'' (by saving him). However, he cares way too much about the detective and has genuine empathy for others. The copying of the reset-investigation was suspicious but he's likely just worried and in the preview he does talk about it with the detective. A criminal would likely either frame the detective for the crimes or silently watch from the sidelines while using the information against him. Sun Ho has no motive to kill people, he gains nothing from it. It is still a possibility though and would be shocking but in my mind he's likely safe.

Webtoon assistant: This guy (Goo Seung Min) hasn't appeared a lot but we know he's just as much a fanboy of the webtoon ''Hidden Killer'' as the detective. He even gives lots of recommendations to Ga Hyun about ''Hidden Killer''. Now for something most people didn't notice. He always brings a giant black bag with him, guess what's hanging in the room of the collected mementos of dead resetters? This guy has a clear motive too. By killing people around Ga Hyun he is ''inspiring'' her to create new content. He is right in front of her, visits her multiple times and yet she doesn't suspect a thing. The nerdy guy look is just something to hide his true intent.

Now that the detective bromance is likely still safe I'll be looking forward to the next episode.

Guys although the murderous detective twist got me shook for a moment I found proof that our detective is in fact NOT the serial killer.
The evidence is in the video-footage itself. If you're curious keep on reading.
I was so shocked at the end that I began feverishly looking for answers since this could endanger the detective bromance plot. I knew that Hyung Jo wasn't guilty of the older deaths so I specifically focused on this one. Then I started looking closer at the video of the murder.

*Evidence to clear the detective of being a suspect*
The body-language of the killer looked like that of our toxic gamer-resetter and it would make more sense for it to be him. I even expected it to be him until they showed the face of the detective.

Now.. If you look closely at the video you'll notice that the killer had a face mask that he only took off after the murder. So the gangster didn't know who killed him at all. The killer is also wearing black shoes (very briefly shown with the blood splatters). Now after the murder we see a scene of a pair of very different shoes stepping back. THIS is the detective sitting down at the computer since he knows the evidence could help prevent his own death in the future.

The detective is obviously used to seeing dead bodies and saw priority in securing the reset-specific evidence for himself instead of immediately calling the police. The detective will be the main suspect if the police investigate so he is hiding his tracks because he doesn't want trouble. How would he even explain his idea to see this criminal to them?

In conclusion, detective is clear of the crime. However, this action might come back to haunt him since Sun Ho is starting to suspect his partner of something (about time too). The preview also shows him as a key suspect so that's unfortunate. I just can't believe Ga Hyun doesn't trust him and it shows why they didn't form a relationship in those 7 months.
Update:
I've seen theories that suggest Sun Ho is the murderer. I don't want to believe it but it is unfortunately a very real possibility considering that Ga Hyun must've made some legit point with her police-station theory. If this is true I'm gonna have to rewatch every Sun Ho scene. There's still lots of other suspicious people involved though so I'm holding out hope.

Here I thought they couldn't shook me anymore. I was wrong, very very wrong. Episode 8 is just crazy. I'm gonna write my thoughts and theory about it in another comment with spoilers. For those that want answers now, read my second comment.

So when is Hyung Jo going to tell Sun Ho about the whole ''fated to die within a year'' thing? I mean.. Sun Ho probably isn't completely safe either. They might skip it but I hope they show it. It's so easy to prove too, just tell him about some important news that hasn't happened yet. Either one of them is gonna die if things go wrong so might as well just say it.
Anyway, I'm scared of Shin now but I know it's all for her unfortunate daughter. She makes such power-moves as a villain. Like imagine just drinking some coffee and she steps in like ''Gruesome death upcoming, have fun thinking about that!''.

I actually appreciate that you posted this because now I know not to watch it (not my kind of drama) but isn't this a spoiler?

And another one bites the dust.
I was so curious that I watched the complete RAW episode and now I have to wait for the translation to actually know what exactly happened.

I'm not in lockdown but I can imagine it must be very isolating. Hopefully you still have some dramas in your backlog to watch! The world will be a different place but I've never been very outgoing so not much will change for me personally. I hope the best for the people of HK.

I'll edit my comment then. Still, the series just wasn't for me.

It's a lovely boran lakorn which can teach you a few Thai words because of the confusion between the older Thai language and the modern Thai language. This is my first period-drama for Thailand and I usually enjoy the first ones the most since I can learn about a culture while watching a good love story. The romance is slow but interesting to watch unfold. First he hates her, then he's weirded out by her, then he gets jealous over the attention she gets and finally he gets protective of her. This series has a bunch of unexpected plottwists that only a Thai drama could have in the latter half.

I hated the dad-character for the rest of the series after his little anti female-rights speech just because he wants to be able to cheat on his wife. This series really represents how women had to suffer back then as married women were possessions instead of individuals. The farang (foreigner) constumes were unrealistic as always (I get it, realistic ones are expensive) but gave me a good laugh at times.

Thanks for the list! Found some new dramas thanks to the list!

Not worth watching for a few funny scenes in my opinion. The premise is great and has lots of potential but it doesn't shine through in the drama.

The acting of the male lead as two different characters (annoyed Thun and wholesome Mek) is really well done and carries the drama forward. Although one thing I just couldn't get over..
Thun's doctor friend saw him after the drowning-event, knows he has supernatural abilities and he just can't accept that past lives could be a real thing? Like how do you not immediately open your mind up to other possibilities after that?

I kinda love how everyone in the drama is just casual about supernatural abilities though. The co-workers are just like ''Oh that's just our demonic boss up to his old tricks again'' when he breaks all the lights again. The ambulance-group just generally accepts that one of them sees ghosts and it's almost never brought up unless it's important to the plot. I also feel like the girl accepted his abilities very quickly, then again she did take a confused stranger into her home instead of taking him to the hospital.

He's probably already happy he upgraded from fanzone into friendzone.

Those are some deep philosophical questions. I personally love the whole loving the soul thing in dramas but I never liked plots where people go from non-related family (I'm assuming they are not biological brothers) to lovers. I'm really just here for laughs, the anxiety and to see the delulu representation in a drama. It's not often that fujoshi-type characters actually get a main role instead of a supporting role.

This would be such a plottwist though. I even thought this episode that the wreckage at the river was the groups bodies before they showed the detective walking towards it. The music stopped so suddenly so I thought they were gonna shock us.. But we have to remember that if the dream-theories aren't correct there's just a car wreckage in a cliff somewhere with all them dead in it within an alternate timeline. Must be a traumatic finding for the police of that timeline.

I'm not sure about anything anymore now but I personally made up the theory that she had them as psychiatrist patients at some point in the future (original future without the group-reset). That would explain why she chose them specifically, she knows a lot about them but hides it. All involved people do seem like the types that could easily go mentally unstable.

She loses her daughter and all those patients also die in different ways in the original future. She went back with an individual reset to the point to save her daughter (possibly from the train-incident?) but somehow that didn't work out. Then she planned the group-reset where she proposed sending the group to the past. Sure she could just go back further herself but there must be a reason (related to failing to save her daughter) that she chose the group-method this time. Possibly she blames them for the death of her daughter (because she couldn't be there to save her) and she feels if she trades their lives in the past then she can keep her daughter.

Aside from the theory, that woman is ruthless, she is completely able to kill multiple people just to possibly protect her daughter. She may claim that it's killing without a goal right now but I personally don't believe that. Also, I'm so grateful for the saving of Sun Ho. The bromance is saved once again.

While it still doesn't reach the levels of Japanese dramas in it's weirdness, it's doing its best. I laughed a lot at their antics. Some of these episodes felt like they were funny/kinda embarrassing and then they suddenly slap you in the face with a plottwist in some episodes (Episode 3 in particular, there are no words). Anyway, it's basically pretty boys doing embarrassing/funny stuff most of the time and the girl reacting like a sane person would. At the final episodes they finally explain the background of the club but you can guess it from hints pretty early on. I didn't expect them to make it so emotional though but it's all good.