Satsujinki×Tensei: Satsujinki no Tensei-saki wa Shin Mamadeshita

Olivia Taylor opens her eyes after being caught and executed for her countless brutal murders to find that she has been reincarnated in a time and world she has no memory of called "modern-day Japan." She soon learns that the woman whose body she is inhabiting, Meisa, has been living a meager life with her preschool-age son, Reo. Meisa and Olivia's memories begin to blend together as she ends up getting caught up in a major incident involving Reo and her common-law husband, Ryuya... Surrounded by friendly faces like the loving Reo and the kind manager of the grocery store where Meisa worked, Natsuki, is this reincarnated monster now destined to navigate this new world as a mother...?! This single mom has no choice but to use the memories and instincts of her former life as a vicious serial killer to confront the evils of the present! (Source: MangaPlaza)