Honestly, only the plot set is the same. The essence is very different cause the FL chases the ML in ELM but the ML chases FL in LO2O and the FL here is much more active and shows more expressions.
But like said, plot set is same so they fall in love online and then their relationship comes offline. Plus its university based.

As reading from the synopsis, we get to know the main aspect of the drama is surrounding ghosts. Hotel del Luna is precursor of precision in drama of showing how exactly a generation long curse of guiding ghosts exists.
I dont even need to explain. We all thought of this drama when we read the summary.

Here how they are connected by wave frequency, the japanese movie has connections in book. Overall its very cute and gives the same butterfly. The basic plot is same but both are different is different ways

Though both the dramas have parallel universe sci-fi shit, Train shows more of a thriller showcase than Derailment while the latter shows more romance.
Even the titles are interlinked.
In Derailment, we see the FL trying to find herself but in Train we see ML trying to find a serial killer. Train has a very subtle romance and isnt the main genre.
But both are very captivating.

Tho the plot differs in many magnitudes and OUAST has more slapstick comedy, these dramas have an undeniable connection. Both are feel good dramas that are there to brighten your mood. We have dumb and idotioc MLs (not really) and smart FLs. Tho OUAST has a SML and no mom element. Its pretty much good.

I know you are wondering why OBS who has a completely different plot is here and usually i would text a bunch of points to explain why both of them are similar but in all honesty, only the essence of both of dramas are same.
Both of the drama come from the same point for me. They don’t just look at the romance part alone. They extend to understand each of the leads and to every decision they made and how they have grown on that. In OBS, we see KYS (FL) and the decisions she made for CW (ML) and for him to grow cause she loved him just like how in HL, SZ understands her heart and what it wants, at the same point maturing to understand what it really takes to fall in love.
Both of them askes the same questions, "What are we?"

These two dramas are like two apples on the same tree. Tho the taste a little diff, essentially they are from the same tree and taste almost alike. Reasons:
1. Smart FL
2. Devilous ML
3. FL falls for some other guy first other than ML then falls for ML (ML was 2nd in line)
4. Spoiler: Massacre
5. FLs have too many similarities like growing up in the countryside, looking after onself alone, having two moms, etc.
6. Imperial Power play
7. Historical Romance
8. ML falls first but FL falls harder
etc etc.

The only difference was that ML in LLTG fell in first sight but in TSOK its gradual and also the fact that FL regressed in TSOK.

How is this and why is this not compared to "Goblin"?
This drama is basically the Goblin of 2022. Now, this isn't about popularity but because of the setting, it is given.
Even though both dramas have huge gaps in the plot, the essence is the same. A rom-com, fantasy thriller with heart-wrenching scenes to cry.
We got killer leads (literally), magic that fulfills, romance to die for, MLs who are imperfectly perfect, awesome FLs with brains, and endings with pain.
Just how did we forget?

SO basically , they have diff plots, like completely diff plots but hear me out k?
Both have comedy
both have slapstick ML
Romance here, Bromance there
Both has Kickass fighting female vibe
Fighting scenes to cool
Embarrassment 101
Cool plots with no thickness

Bonus: Yamazaki Kento, Baby!

For many obvious reasons, the plot sounds the same.
Ghosts- check
Three leads- check
Different ways but same purpose- check
Deaths- check
Police- check
I mean i can keep on going but you get it, right?
Same to same

the plot is basically the same but this drama is more concentrated more on friendship and all that family strength blah blah. this is drama is like the future version of racket boys but i doubt whether their personality are the same. its an amazing drama, trust me on this!

To a certain point, it gives the same vibe. I wouldnt say that this drama is similar to Love Alarm though. Love alarm is much younger and teen concentrated while this is more of a simpler (or complicated) and plainer (or sassier) version. This drama also gives an insight to BL love which Love Alarm doesnt have. Be4 i explain too much in detail, check it out for yourself.