My cat became a monster

Death has always existed closer to me than it has for others. Everything important to me has disappeared and slipped through my hands. Yori is a young lady in her 20s who's trying to get through life after the death of her cat, Yuki. One day, a beautiful white-haired youth appears before her claiming to be Yuki?! Is this man who he says he is? Or is there something else Yori is missing?