"Erica-san... won't you become family with me?" After losing his mother at a young age and growing up without experiencing a mother's warmth, Ryota developed intense feelings toward women who reminded him of maternal figures. He becomes obsessively attached to Erica, his cousin and private tutor. During one lesson, he suddenly learns the shocking truth: "Erica-san has a boyfriend." The emotions welling up inside Ryota soon spiral out of control.