There is a vampire character in the series called Shinobu (Maaya Sakamoto). In the first series she was silent, in this she appears occasionally, emerging from Koyomi’s shadow, where she now resides. She does speak to Koyomi and also has a fetish for donuts. It appears she no longer needs to feed on blood – possibly due to her symbiotic relationship with Koyomi – but can regain some of her powers when she does feed on blood (in the case of the series, on Koyomi’s blood), and when she feeds she morphs from a child’s form to an adult.
|emerging from shadow|
The imdb page is here.