If you want a mature story, with very deep characters I highly recommend Monster. It's kinda like a psychological horror movie and definitely one of my favorite anime/manga. There are no school girls, fan service nor anything like that. Plus if you said you like conspiracy then this is the thing for you.
Btw, my sig is from that manga.
Edit: if you want something more over the top like Berserk you should watch Claymore, they are relatively similar.
Nintendo and PC gamer