Shuuchaku Kono onna kara nigerarenai

Here is the translation of the synopsis. I have captured the creeping psychological horror and the escalating tension of the story.

Koharu Sakai was living an ordinary yet happy life. Surrounded by a precious family—a timid but kind husband and a lovely daughter in the prime of her youth—she thought her days of peace would last forever.

However, a reunion with a former junior high classmate, Kanon Shirai, causes Koharu's daily life to quietly spiral into madness.

Kanon was the bully who once tormented Koharu and drove her into deep isolation. Koharu tries to tell herself that it was all in the past, attempting to break free from her trauma. But for some reason, Kanon begins to relentlessly encroach on Koharu's life.

She moves into Koharu's neighborhood. She visits Koharu's workplace. She even transfers her own job to be closer to Koharu's home... Using her natural charisma, Kanon slowly turns everyone around her—her mom-friends, her husband, and even her own daughter—into devoted believers, stealing them away one by one.

Unable to grasp Kanon's true intentions, Koharu finds herself being driven into isolation once again. What is Kanon's goal? Why is she stalking her?

And then, Koharu realizes the terrifying truth. This isn't just "bullying." This is... "Obsession."