As Her Summoned Beast, Must I Bow Down and Obey?

(Gender-bender, 1v1 pure romance. The protagonist is a psychopath who gradually turns toward goodness.)

A strange deity summoned her back from Hell. Filled with resentment, she wanted to unleash it all upon the person she had once loved most. That person had killed her, and all their wonderful memories together hadn't changed the outcome.

The deity started a game, and they became its players. Paired together, each became the other's summoned beast and summoner, sharing a life. As a result, she lost her chance for revenge.

But even if she couldn't get complete revenge, there were plenty of other things she could do: torment, pain, destruction. She would never accept this.

The white-haired, red-eyed girl wrapped a chain around the neck of the black-haired girl before her, contemplating what torment to inflict today.