Originally known as Kiss-shot-Acerola-orion-Heart-under-blade, Shinobu Shinobu is the strongest of the strongest monstrous "vampires", having lived for almost 600 years, and is a beautiful, regal, and sexy ojou-sama. She is a beautiful, noble, and sexy vampire. She is called "me" and "you" in the literary language. She is known as the "Iron-blooded, Hot-blooded, Cold-blooded Vampire", "Monstrous Killer", and "King of the Monstrous", and has the power to destroy mankind on her own. In the story "Hurt Story", he came to Aryangi's city and was crippled by four hunters, but survived by sucking Aryangi's blood. After losing her powers through the intervention of Shinobano Bleat, she took on her current loli form and changed her name to Shinobano Shinobu ("Shinobu" is the name given by Shinobano, meaning "underneath the sword"). The name "Shinobu" was given to her by Shinobu, meaning "a heart underneath a sword", which is synonymous with her original name, Heartunderblade), and she has to suck Riku's blood on a regular basis in order for her to exist. In fact, he also likes Riku, and even agreed to die together, and attaches great importance to the special bond with Riku. After the incident, he refused to speak for a period of time because he was angry with Riku, but after that, he lurked in Riku's shadow, and then reconciled with Riku in "The Fire Rei and the Bee", and began to speak again. She is very fond of Mr. Dount doughnuts, and is often blackmailed by Calendar.

Can create matter, make video games, clothes, and even time travel. After sucking Calendar's blood for a while she was able to regain some of her powers and become more mature, and could have fully recovered from this but didn't.

In "Cat Story (Black)", he is first introduced to donuts and engages in all sorts of cute endeavors for the sake of donuts, but is unfortunately dismissed by Calendar as a hallucination.