An Ibaraki Prefecture man drove to a police station Sunday with a woman's corpse wrapped up in the back seat of his car, and he confessed to killing his girlfriend.
Katsuya Yamaguchi, 41, of Tsukuba, was arrested at the Ushiku police station in the morning. He said he strangled the woman, whom the police believe was Chinese. Her body was found wrapped in a blue plastic sheet.
Police suspect the woman was slain the previous day.
Police said Yamaguchi and the woman first became acquainted as colleagues several years ago while they were working for the same employer.
The Chinese woman had complained to the police in late April about "problems related to her relationship" with Yamaguchi, and the police said they responded by verbally warning him.
The woman did not bring any more complaints to the police, but they suspect she had asked Yamaguchi for "monetary assistance," which led them to believe their relationship continued before her death.