Regeneration

Regeneration is a special ability of vampires which accelerates healing of wounds.

Vampires can instantly heal the injurues they received, but it does not deprive the feeling of pain.

After Raquel Alucard bit Naoto Kurogane, he gained this ability, and also became stronger and more enduring.

As discovered by Naoto, his vampire regeneration heals injuries and fractures he gained, at expense of Raquel's vitality. Therefore, the sores received while Raquel was part of Spinner Superior did not recover, nor did his hand that had been severed, even after rescuing her.