@Dri I'm not particularly sure when it started becoming popular in manhwas, but I do know it's been a trend ever since the popularization of isekai. Mainly to appeal for a more female audience compared to most other isekais.
The trope seems to become popular because of the interesting...
This story is quite amazing and very well put together for such a concept. I don't like the yandere trope too much, but they put such a spin that it almost makes them more human and it's refreshing.
An interesting detail that I absolutely love done by the author is their great usage of names...