It's not that I haven't enjoyed it that much xD It's because the story is a bit sad and some parts are hard to see

Some other animes also have parts that are hard to watch... I'll watch episode 1 again... because now I actually understand most things he has said... In the beggining I was like wtf is this agency/organization (dunno what word was used in english sub) he's always talking about? It took me time to realize he was just kidding. Well, that's just one example.
and about sad things I wouldn't rewatch... sorry for the spoiler but you'll understand what I mean
http://sphotos-a.ak.fbcdn.net/hphotos-ak-ash4/486926_410030439069456_1282499023_n.jpgthat was just too hard to watch xD