Rafael Costa is a supporting character in the anime Kujira no Josefina and the father of the protagonist Santiago, usually called Santi, and of his younger sister Rosa. He is married to María, and the household also includes the children's grandmother and the family maid Benita. Rafael works as a veterinarian, a detail that appears when Santi visits the clinic where his father practices.

In terms of personality, Rafael is presented as a man of strong and firm character. He is a strict parent who does not hesitate to discipline his children when they misbehave. When Santi, reluctant to attend school, caused trouble at home, Rafael punished him with a spanking and by denying him dessert at dinner. Despite this firmness, he genuinely cares for his wife and has a deep love for his children.

His role in the story is mainly that of a parental figure in Santi's everyday life. He takes part in key family moments and takes on the responsibility of guiding his children through difficult lessons. When the children's grandmother dies, Rafael helps Santi and Rosa understand that people must eventually depart, giving them an early introduction to the ideas of loss and mortality.

Rafael's relationship with Santi is meaningful to the boy's growth. Santi initially keeps some emotional distance from his father, and Rafael himself appears somewhat remote within the household, but over the course of the series Santi gradually comes to know and understand him better. This growing connection is part of Santi's larger movement away from the imaginary world of his whale friend Josefina and toward the real world and his family.

Rafael does not possess any magical or special abilities. He is an ordinary, hard-working professional whose importance comes from his role as a constant parental presence. His development is seen mainly through his changing dynamic with his son, as the strict but affectionate father becomes a more familiar and approachable figure in Santi's life.