Assassin wa Fushi no Majo o Koroshitai

Lalanica is an immortal witch living a solitary life deep in the forest.

One day, after hundreds of years of isolation, she finds a dying boy. With nowhere else for him to go, she names him "Nox" and decides to care for him for a while.

Thus begins their life together. As he grows, Nox falls in love with his savior. However, Lalanica, knowing all too well the heartbreak of being left behind by mortals, refuses to accept his feelings.

Unable to give up, Nox agonizes over the dilemma until he reaches a singular, shocking conclusion:

"I promise I will kill you... so please, marry me."

Though stunned, Lalanica tries to convince him that ending her life is impossible. Undeterred, Nox leaves the forest, determined to find a method to kill her.

Years later, when he finally returns to her side, he has become an assassin cloaked in the heavy scent of blood and death—?