Yamato Nadeshiko Shichi Henge (Japan, 2010, for so many reasons, but there is also a Halloween episode)
School Tales The Series (Thailand, 2022, totally agree with cutearisu on this one, is nice that it's on Netflix)
Gourmet Detective Goro Akechi (Japan, 2020, dark comedy that turns uber creepy)
Let's Fight Ghost (Thailand, 2021, because the leads are made of so much awesome, also on Netflix)
Heaven and Hell: Soul Exchange (Japan, 2021, Issei Takahashi is brilliant, and it's on Viki)
I don't watch a whole lot of dark dramas, but these are dark paired with something else, except for School Tales, that's just dark. Have fun watching and rewatching some spooky dramas!