Saya's amnesia isn't a plot device, it's the real story, and the show knows this will destroy you when the truth arrives. Every episode peels back who she actually is, what she's actually done, and what the Red Shield actually wants from her, and none of it lands the way you expected it to in episode one. The monsters are secondary to watching a girl spend fifty episodes learning she's the thing she's been hunting, and by then you've loved her too much to look away.

Saya Otonashi seems like an ordinary high school girl living with her adoptive family in Okinawa, except that she suffers from anemia and cannot recall anything of her life before the past year. One night at school she is attacked by a creature that drinks human blood, and a mysterious cellist named Haji comes to her aid and gives her a Japanese sword. The monsters are Chiropterans: immortal beings that can change shape and pass as human while feeding on blood. A group called Red Shield has been waging a hidden war against them, and now Saya and Haji join that fight while searching for the truth about who she is. Blood+ mixes supernatural action and horror with drama and an ongoing mystery about the heroine's forgotten past.