Tatsuya was born as the second son of three brothers. His mother, Yumi, gave the impression that he was a quiet child who didn't assert himself, but... One spring, his older brother got a job and lived alone, while his younger brother enrolled in a boarding school on sports recommendation. My father moved away from home and his life changed in a hurry, and a mother and child began to live together. Yumi feels a sense of loss as the bustling house suddenly becomes quiet. Seeing her mother like that, Tatsuya feels an indescribable jealousy and tries to regain her mother's affection, which he couldn't monopolize until now.