You need to pay attention to the shading and contrast to bring out the depth. Also, focus on the facial features and expressions to make them look unique.
In the 'Black God' manga story, Keita Ibuki is a key character. He is an ordinary boy who gets thrown into the extraordinary world of Contractors. Kuro is another significant character. She is a Black God, and she has her own set of powers and a complex personality. There are also other characters who are Contractors, each with their own unique abilities and roles in the story. They interact with Keita and Kuro, and through these interactions, the story progresses.
Asta is really interesting. He's born without magic in a world that highly values it, but his determination and unwavering spirit make him stand out. His anti - magic sword and his unique fighting style are cool too.
Well, usually, animators use a combination of digital tools and artistic skills. They might study the character's design and personality to determine the appropriate colors.