BubblesPink

So far the Japanese version has stuck pretty close to the webtoon, things have been tightened up/shortened since there's only 10 episodes, but many of the major plotpoints from the webtoon are there.

I haven't read the webtoon in 1.5 years, but in the webtoon (and kdrama) Ji Won/Misa is killed by being shoved and hitting her head on a glass table, not being thrown from the apartment. In that version Ji Hyuk (Wataru) walks into the apartment right after it happens.

In the kdrama Ji Won and Ji Hyuk discover they're both from the past because they mention BTS songs that haven't been released yet. Ji Hyuk is also much more involved, working behind the scenes with his friends (that don't exist in the webtoon) to help Ji Won get revenge. In the webtoon, Ji Won doesn't discover he is from the past until much later, when she reads a letter he left hidden just in case something happened to him (I think). Ji Won also conducts her revenge more solo in the webtoon, similar to the Japanese version.

Sumin/Reina's motives are explored more throughout the webtoon and kdrama, and we see her thoughts a lot more. In the Kdrama, Minhwan (Tomoya) is pretty evil and abusive towards Ji Won from the beginning, in the webtoon he's more similar to the Japanese version, an idiot who's using Ji Won, but he's actively looking to cheat and doesn't really care about her.

There are more differences, these are just the ones I remember off the top of my head. I think the jdrama has been more faithful so far, I ended up dropping the kdrama around episode 10 (when they introduce Ji Hyuk's ex-girlfriend that wasn't in the webtoon). If I hadn't read the webtoon I probably would've enjoyed it more, but I couldn't stop comparing it lol.

Oh also the animal Wataru/Ji Hyuk took care of was a cat, not a turtle. That's the one change I don't like haha.

As a fan of the webtoon, THIS is the adaptation we deserved. The Korean version didn't capture the essence of some characters and changed so much from the original it was almost a different story. The Japanese version is exactly what I envisioned when reading the webtoon, and the changes made feel natural to the story and aren't as jarring. I love this version of the ML and FL so much more than the kdrama version. If you're a fan of the webtoon I highly recommend watching this version!

Age is one major factor, but also Jia Xu was someone they knew and considered family. They trusted him as another older brother figure for ZhiZhi and so seeing them together romantically was something they had a hard time with. For Sang Yan, Yi Fan encouraged him to work harder at school and get into a good university, and they were both the same age, so they see Yi Fan as a good influence on Sang Yan and an appropriate partner.