Plot pls?

I not good at summarize the plot, but I can give an idea...it is about Love fill with murderous intention, to kill the one u love, the more u love love someone the more u want to kill them, if is like an infectious disease, spread from another to another person, in this case MC has an unrequited love toward the girl and always want to kill her because he got infected from the middle age man.
















Spoiler here : the girl is not normal too in the later chapters.