Phantom mother, a good mother with short legs

Tsubaki, a mother who is proud of her slender, beautiful legs, and her son Yusuke, have at some point started to have a relationship even though they are father and son. The relationship between the two was hidden from his father and older brother Mamoru, and was a secret between the two of them. However, Yusuke loves his mother's beautiful legs so much that he gradually begins to boldly pursue his mother's body, and it is only a matter of time before he finds out. And finally, Mamoru discovers the relationship between the two...