Blood+
Blood+ took the basic image from Blood: The Last Vampire, a girl with a katana hunting Chiropterans, and turned it into a fifty-episode family tragedy that moved from Okinawa to Vietnam, Russia, France, England, and New York. It aired for a full year beginning in 2005, which gave it room to be slower than people expected. That pace is the point. Saya is not collecting monsters of the week. She is recovering a life that was taken from her in pieces, and every answer makes the family around her more complicated.
Adult Swim brought it west in 2007, where it became one of those shows people either followed every week or lost completely after missing three episodes. The opening themes changed, the locations changed, the conspiracy kept widening, and Hagi remained Hagi.
Do not confuse it with Blood-C. Same name, different wound. Blood+ is the one that takes its time.
Guides and reference pages for this series. More coming.