Wracking my brain and, I'm struggling to think of what the answer would be... I guess it depends on what one considers 'dark'? Like... ? Scary, horror, violent things...? If so, I'm very sensitive to things like horror so despite being allured by horror concepts, I've never been able to stomach things that are tooo scary...! My mind has always been very permeable, and I often dream about what I look at, so as a kid I was desperately trying to avoid having nightmares by focusing on more 'pleasant' worlds... like pokemon and hamtaro. (To the point where I couldn't even played games I really liked... I had to stop playing OoT & MM because of chronic nightmares spawned from them kfkfk... I'M BETTER NOW but it was a problem when I was under ~10 years old.) It took quite a while to be able to work my way up to psychological horror and artsy adult movies... [squints.] Maybe.......... Elfen Lied........... was as buck wild as it got, around ~14...

But if you mean 'dark' as in... fanworks, fan content (uhh age gap incest noncon etc...) Then. [my mind tabs through, childhood of kid Bird searching for 'Link and Zelda kiss'] hmmmmmmmmm......... Hm. Perhaps taxonomically it was when I discovered there's a lot of pokemon porn out there in the world. I was like ~12 for that... Ooh but it feels kind of silly to call it dark or weird. Since even tho it was ferals/zoo the content itself didn't feel dark in nature, and. My reaction to seeing it was just 'yassssss god doujin of girl being railed by zebstrika wooooo!!!!!!!!!! Epic.' What I was writing/drawing happening to my own OCs at the time was far more ah, gritty at least, like lots of stuff happening there, but that doesn't count as 'consuming'...

The takeaway here might be that, I was already engaging with '''dark'''' fantasies in my own head well before I saw fanwork of it/was able to stomach it in books/movie/TV. So I don't think I have a very strong impression of my 'first' experience with it...!