• Every single fox of Team Korei has darkened fingers and claws.
  • Mayin, more than them, has his arms completely darkened. So when he shows his hands from under the sleeves of his clothes, both his hands are completely pitch black.

This phenomenon is called "Rage Unleashed".

• ⬆️ It's also the name of one of my headcanon forms for Koenma but we won't be talking about him in this space since it's for other characters.
• Koashura also has darkened limbs, which is a normal occurence between Danavas. When he transforms, though, the form he takes with additional arms (up to eight) and markings around his skin, is called "Karmic Release".
  • The foxes have dark fingers and Mayin has dark arms exactly because of him. As Koashura's main source of energy is negative feelings, he also enjoys seeing them partake into them; thus, the more anger, desire for revenge, sadness or depression they feel, the more dark their limbs become.