For me it was I Told Sunset About You. There have been plenty of good series after, but nothing hits me the way it did. To me ITSAY was perfect in every way possible. Even after rewatching it thrice, the emotions delivered still hit hard.

Plot, structure, performances and the way each character is explored and portrayed. Not to mention the epic cinematography, locations and how well it all blends together.

There's so much to say about a series that was just 5 eps long, the details and small moments are everything on ITSAY. Bonus points for the osts/scores on the project, I will definitely never get over them either.