Ero Kakusei-jutsu de Kaa-chan to Muchakucha Yattemita

A son finds a mysterious book about 'erotic awakening' left by his late grandfather. He uses it on his mother, causing her body to become extremely voluptuous and her libido to skyrocket. They engage in intense sexual activities over several days, with her body continually adapting to his desires. The son continues to have intense sex with his mother, who has been transformed by the spell. They engage in various sexual acts, and the mother becomes completely devoted to him, even calling him her 'husband'. The story concludes with her seeing him off to school after a morning session.