One month after my father remarried Tsubaki, a beautiful, kind, and gentle woman, my brother and I were completely smitten with her. Though she held the role of a mother, she also carried undeniable feminine charm, and my older brother, in particular, had fallen deeply for her. My brother excelled in both academics and sports, and I felt a quiet resentment toward how especially fond Tsubaki seemed of him. Before long, behind our father's back, their relationship grew increasingly intimate—so much so that they began taking baths together. One night, Tsubaki quietly approached the bunk bed where my brother and I were sleeping...