Thread:Narukami-nara/@comment-32447612-20170701110339/@comment-29781768-20170701131945

There is :

Sometime before Subaru got summoned to Lugnica, She took the Witch Genes of Envy, which we're imcompetible. Because of this, Satella created a second personality 'Witch of Envy". Witch of Envy and Satella are very different. Satella is nice and forgiving while Witch of Envy is harsh and "envious". More isn't confirmed. There is no more information about why Satella loves Natsuki Subaru.