I know how general this request is, but I really can't find any exciting anime anymore. I have been watching too much slice of life and romance. I need a good thriller that keeps me hooked and excited throughout the show. Something that makes you stressed and engrossed in the plot. Something not popular since I probably have watched it and give me multiple suggestions thank you since I would have probably watched 99% of all that is about to suggest.
Gunslinger Girl Mushishi Phantom: Requiem for the Phantom Darker than Black Arslan Senki Nurarihyon No Mago Baccano(same author as durarara) Youjo Senki 19 days Black Blood Brothers Jigoku Shoujo Elfen Lied Tokyo Magnitude 8.0 Angel Beats Death Parade Claymore Baka to Test to Shoukanjuu Kakushigoto Sound of the Sky No Game No Life Ghost Hunt XxxHolic Aoi Bungaku Series
Plot-heavy thriller immediately makes me think of Monster. But I bet you've seen it already. If not, def go see it. After browsing through some anime lists, some of which I don't agree with, here are some more titles: Shiki, Another, Promised Neverland. It just seems unlikely you haven't seen any of those. They're kinda rare. Studios like going for cash-grab harem anime...
Oh my lord Gankutsuo is the shit. if only for the OP theme. Its been a hot minute since I have seen it but anything relating to Monte Christo is a banger for me.