Seiji was the second son in a family of three brothers, and to his mother Reika, he had always been an easygoing child. However, one spring, his older brother began living alone after landing a job, while his younger brother entered a boarding school. Their father was transferred to a remote work assignment, leaving the house suddenly quiet. From that point on, Seiji and Reika began living together as a household of just mother and son. The once lively home had changed completely, and Reika began to feel loneliness and a sense of loss. Seeing his mother this way, Seiji was filled with regret and emptiness, his heart stirred by the desire to reclaim the mother's love he had never fully possessed.