In the future, the earth suffers an enormous overpopulation problem, all due to one \"megaplayboy\". An agent, Aoi Karin, is sent back in time to avert this disaster by altering the DNA of the megaplayboy, who turns out to be an ordinary high school student, Momonari Junta. He has a \"female allergy\" which stops him getting anywhere near girls, but all that changes after Karin accidentally shoots him with the wrong DNA control medicine.