The links to opposite worlds

Once every few years a link between worlds will be born but have never lived passed the age of 2.In tell one day in both worlds two babies were born ,one had long white hair with the front part being blue and the other was the opposite with long(but she cut it short when she got older) black hair with the front part being red.Their names were Aisu and Kasai.Aisu was friends with everyone and was always trying to help in anyway.Kasai on the other hand want people to be hurt and hated everyone/everything.But unknown to them their lives would change forever. On their first day of high school!!