spoiler:

Did you know that theyre sister? the red hair and black hair is sisters. The black hair thought that the red hair her sister abondon her so she grew hating her sister. But the black hair is sick and she doesn't know that the red hair is working her ass off to pay for her bills. at the hospital. The black hair died hating her sister. Then she got summoned in that harem world. And then she asked the god. "hey bring my sister here" and that was the story..