Extracurricular was my second kdrama, after Crash Landing on You. Very different, I know! Lol! I wanted something less romantic and found this as one of the recommendations given so watched it without giving much thought. Finished in 3 days and wow... I am reeling in from the show. Definitely does not have the 'feel-good' ending that I get from other k-dramas i've subsequently watched. And that is clearly what will set you thinking.
The characters are believable, though not very relatable (esp the ML). But you end up rooting for them even though they are clearly not doing lawful things. You just keep finding excuses for their wrongdoings, and just feel horribly sorry for them that things just spiral downwards exponentially after a few episodes.
What kept me going I guess was hope that the ML will find a way out of his abyss. I had hopes for FL to be the guiding light but she is anything but. Also, circumstances had forced ML to be in that sticky situation that he had delved in so deep, he does not know the way out anymore.
Pretty dark and twisted show, but I enjoyed it. Though I needed something lighter after that to lighten me up.
Side note, I watched Itaewon class after this kdrama and surprisingly found the ML as a supporting role.

Watch it! There is also a bit of gore... I don't think I can stomach anything more than this after this kdrama!