Japanese authorities arrested the suspect, initially identified as Juan Carlos Pizarro Yagi, on Nov. 30, 2005, eight days after finding the strangled body of Airi Kinoshita Nov. 22 in a vacant lot in the western city of Hiroshima.
Local police later determined that he had entered Japan on a fake passport in April 2004, and that his real name was Jose Manuel Torres Yagi, Kyodo News agency said, citing the indictment.
In Tuesday's ruling, Yagi, a 34-year-old Peruvian of Japanese descent, was handed a life prison sentence by the Hiroshima District Court, court spokesman Masuo Terasaki said.
Prosecutors had sought the death penalty. Defense attorneys had asked for leniency, saying Yagi didn't intend to kill the girl and felt remorse, Kyodo reported.
But Judge Hiromichi Iwakura found that Yagi had a definite intent to kill and sexually assault the girl, Kyodo said.
Yagi's act was "nothing but mean and cruel," the agency quoted Iwakura as telling the court.
Kinoshita said he would appeal to a higher court, according to the AP.