My Puppy Grew Into A Tyrant

Luna is a low-born, grey-winged girl. She saves a dying boy named Ragnar. Ten days lost in a time rift cost her ten years - she returns unaged, and Ragnar now commands the empire, still hunting for her. His curse: every time he loves her, it kills him. So she walks away. He'd rather die than let her go. Ten years. One cure. One wedding.