Jiro's ten-year-old, younger brother, who does not seem to exhibit powers of a vampire, such as the "Hide Hand." Although, he seems to have an extremely high pain tolerance, as he is thrown into the ground and walls without injury in almost every episode. As commented by Mimiko, he does not appear to be the brother of Jiro since he is not hurt by sunlight nor water, unlike Jiro. Another fact is that they look totally different from each other: Jiro is tall, has black hair and grey eyes, while his brother is short, has blond hair, and blue eyes.
Kotaro stated that they are brothers because they are the last two remaining vampires of their special bloodline. They both carry goggles around their necks. He has the same speech pattern and bears a striking resemblance to Jiro's former lover, Alice. Later, it is revealed that Kotaro is actually the reincarnation of Alice. He has no special vampiric powers because he still has not recovered the sage's memories from Jiro.