Alright, this anime aroused such a mixture of feelings for me. I was constantly on the edge of my seat—so points for an adrenaline rush. But there were just WAY too many inconsistencies within the plot. I have to say that when it comes to completely disturbing ways to obliterate your innocence, this anime loses to no other. I suppose I'll just go down the list in addressing my grievances.
The story was extremely interesting, a sort of spin on futuristic mutants from X-Men, but with love triangles which are far more twisted. Elfen Lied did a good job of explaining character backgrounds, and there was usually (emphasis on usually) logical explanations for the events. But for the life of me I could NOT fathom how any amount of sick childhood love could justify gruesome slaughter. News flash: Most people generally don't have romantic feelings for the people responsible for murdering their family. And let me just comment on how out of place the whole "two-personality" deal was. Switching from savage killer Lucy to a blissfully ignorant cat-like thing who can only cutely utter "Nyu!" and blushes when fondled was just mind-boggling. I get the whole comic relief aspect but it was too forced, and slightly crude to say the least.
The music was incredible, and I appreciated the author's commitment to staying true to the German Folktale aspect of the plot. The Latin opening and background music was a nice touch and showed thoughtfulness. While I'm on the topic of things I enjoyed, this anime had no lack of emotional prowess. Extremely feelsy. In fact one of the scenes was so sad it made Jack's heartfelt goodbye to Rose in the "Titanic" seem like a minor lover's quarrel.
Characters. Now this was an iffy subject for me, because I either loved the character or I completely loathed them. Lucy/Nyu, despite her questionable personality, had such a compelling story and passionate feelings, I was able to overlook her sociopathic murder spree. Mayu was an absolute doll, your average rogue who you have a soft spot for immediately. I did enjoy Kohta most of the time because at least he attempted to be courageous, though I couldn't disagree more with how he handled many situations. However, Yuka, Kohta's cousin and childhood friend, was a nightmare. Her weird obsession with Kohta disgusted me, and her hidden malice for Lucy due to her jealousy made me want to punch my screen. Several times. A horrible heroine who couldn't deal with her feelings in a normal way. But then again, this wasn't a normal anime...
All in all, this anime was indeed enjoyable, thrilling, and emotional. If you can stomach the gore, and ignore the illogical decision making, this anime would be a great watch.