Impossible bunk bed - Close-up stepmother incest

It's been a month since my father remarried a beautiful and kind woman named Tsubaki-san, and we brothers were falling in love with each other. Before she was a mother, she became aware of it as a woman. However, he was also frustrated by Tsubaki, who was so loving about his brother who is versatile in both studying and sports. The relationship between my brother and Tsubaki was heated up, stealing his father's eyes, and eventually they started taking a bath together. One night, Tsubaki secretly came to the bunk bed where we brothers sleep...