Kuru Kuru Coeur
Original title: くるくるくーる
The protagonist visits his childhood friend Kirara at the prestigious Extraordinary Science Laboratory, or Exlab.
On one of her lab's table lies a mysterious and suspicious-looking device. As the protag activates the machine, it turns out it actually is a mechanism capable of changing the gender of a person!
Download and install instructions
Game is available for direct download from various file storage providers. Install instructions can be found on developer website.