The main character of this hentai, Junpei, grew up without a mother and found his only source of support in Marie Sanada—the caring and incredibly attractive mother of his best friend. He often visited their home and was always captivated by Marie-san’s kindness and femininity.

One day, Junpei accidentally saw Marie naked while she was awkwardly changing clothes. Unable to control his arousal, he begins to masturbate right in the hallway, but just as he climaxes, Marie catches him red-handed. Contrary to expectations, instead of causing a scene, the embarrassed Marie suggests to the shocked young man that they keep everything a secret from her son and begin secret "training” sessions in bed to prepare him for future relationships.