Since her childhood she has had a creature (that only she can see), which she named Noir, who follows her everywhere. Noir is only able to touch material things when she is close to Josefina, and Josefina's health is better when she is close to Noir. They have a friendship like relationship, but Josefina is also very grateful to her, because Noir saved her life.

When she was younger, she developed a skin cancer which rapidly expanded to other vital organs, she was hospitalized and there Noir found her, drawn to her like a moth to a flame. Josefina was able to see her and they started talking with each other, they decided to make a deal so Josefina can live and Noir can interact with the physical world.

Her sickness is encapsulated in the dimension where Noir comes from, where time works differently. This makes Josefina be not sick and sick at the same time, technically both in a state before she got cancer and dead simultaneously. As a secondary effect she can see the other shadow creatures like Noir, but not as clearly as Santiago can, so most of the time she just ignores what she can perceive.

She is Mauricio's girlfriend, and only speaks with Santiago because he is Mauricio's friend. At the beginning her and Santiago didn't get along with each other, but they start to bond a little when they discover the other can see the weird shadows too. Even so, Josefina takes any opportunity she has to insult and taunt Santiago.

She lives with her father and sees her mother on the weekends. Her father blames her mother for her sickness and fighted to gain the custody.
She is very foul mouthed and doesn't let people tell her what to do. Her favorite sport is football (soccer) and practices it with Mauricio habitually, sometimes Santiago joins them at the neighborhood's square.