After separating from her husband and living apart, Yoko noticed her only son Ken's behavior taking a turn for the worse. Pained by his transformation and growing increasingly distressed, she watched helplessly as Ken, already hot-tempered, became disliked by his classmates. When he finally rebelled, he was betrayed by the very friends he trusted. Devastated, Ken transferred to his father's distant workplace. But the tragedy didn't end there. One day, as Yoko stood alone at home, the doorbell suddenly rang...