A former inmate who 3 1/2 years ago confessed to a murder committed in 1980 was arrested Thursday on suspicion of using amphetamines, police said.
The arrest came less than a week after 53-year-old Kenichi Ota was released from prison.
Takamatsu Prison released Ota on Saturday after he completed his prison term for violating the Amphetamines Control Law.
In April 2000, Ota sent a letter to police in which he confessed to murdering a 21-year-old man in Nagano Prefecture 20 years earlier.
Up to that point, police had treated the Nagano case as a suicide. After the confession, no arrest was made because it came after the 15-year statute of limitations had expired.
Last week after he was released, Ota met with the 67-year-old mother of the murder victim and apologized.
According to Aichi Prefectural Police, Ota was arrested Thursday after being questioned by police in the city of Shinshiro.
Investigators had been dispatched to a rural road Wednesday night after being alerted by a local resident that a car had run off the road.
Upon arriving at the scene, they found Ota, who appeared to be unsteady on his feet. They asked him to accompany them to the police station, where a urine test showed traces of amphetamines.