Super Ultra Mucchin Puripuri Cyborg - Marilyn DX

Kenji was just a regular teenage boy who had a normal life, which included a girlfriend. However, everything changes when one day he comes home and discovers that his insane father has created a female cyborg. His previous attempts failed because he used an artificial brain; this time, to avoid this mistake, he takes out his son's brain and puts it into the cyborg. Poor Kenji gains a second life - as a beautiful artificial woman, whose task is to oppose a dubious world government organization.

[From Mobygames]