There's A Fine Line Between Love And Hate

Everyone stops aging at 18 until they meet their soulmate.

Julius, now 581 but only aged (mentally as well as physically) to 18, has spent almost his entire life looking for his soulmate so he can kill her and live forever.

Kassy, 18, has absolutely no desire to live any longer or shorter than the average human life. She is desperate to find her soulmate before her 19th birthday to make sure that happens.