A side story from the original: Ai wishes to be a real woman, after thinking that she had dreamed her sister doing with the doctor. On the other hand, Ryuji Hirasaka wants to have his pervert experiments trial on Hikaru. Instead, the doctor become a savior to Hikaru & Ai for his new invention having both sisters doing it to one another and Ai thought that it as a dream... The last episode ends as the doctor and his newly wedded bride nurse, Ren, went exile to a village to continue his medical practice... and of course his experiment only on his bride.

(Source: Anime News Network)