From MangaHelpers:

Shun Yanahara is a pretty normal first-year high school boy. His grades are not terrific, he's not very popular with girls, and he plays soccer with his school's club. He's often felt like someone was watching him, and, strangely enough, he's right. On a far away Earth-like planet known as O-pa, there is a civilization made entirely of women. One of them, a scientist named Lib Myura, has fallen in love with Shun. She and her two colleagues have created an illegal male human robot, called a synchroid, which they intend to fill with Shun's consciousness.

However, things never go exactly as planned. They successfully make contact with Shun, but it isn't just his mind that the synchroid shares. Any injury the synchroid sustains is inflicted on Shun, back on Earth. What's worse, when Shun is not actively inhabiting the synchroid, it reverts to a crazy sex-crazed pervert. Things only get more complicated when Myura's illegal research is uncovered! Now the three scientists and the sometimes-crazy synchroid are on the run, and Myura knows that if the synchroid is destroyed, she'll be guilty of getting the man she loves killed! [tethysdust]