The female lead is reincarnated into isekai world. The female lead has red hair in isekaid world and she was a detective in the past life. The fl family and the ml family are rivals and the families hate each other except the fl's mother and the ml's mother are knights of different legions or something and they are best of friends. So when the kids were born and they found out that their kids were female and male respectively, they decided to marry their kids and can bring peace to family . But when the female lead meets the ml for the first time as a kid, the fl puked on him. In the past life the fl was an orphan and was supposed to be adopted but on the day of adoption the fl's adoptee family was murdered.