Everyone is gone, apart from them.

You wake up one morning, you follow your normal schedule. But you realise there is no one around. Your family/friends are missing. Everyone is gone. But then your phone gets a message, its off your ex partner. You're stuck on an empty earth with the person that either caused you pain, or you caused them pain. Decide whether to survive with them, kill them off and survive by yourself. Fall in love again? It's your story.