Prosecutors have sought the death penalty for a man charged with murdering a woman in 2011 and causing his girlfriend's death in 2009.

Keiji Hayashi, 43, is facing a lay judge trial in the Nagoya District Court over the murder of restaurant worker Madoka Morioka, 27, in Aichi Prefecture in November 2011, and causing his girlfriend, Eri Asano, 26, to kill herself in July 2009.

"The crimes are extremely atrocious as he used the victims to gratify his desire and did not treat (each of) them as a person," the prosecutors said in a statement Wednesday.

Hayashi allegedly strangled Morioka with his hands because he believed she was obstructing him from becoming intimate with another female worker at the restaurant where the victim worked. He then allegedly dumped Morioka's body in Lake Kuzuryu in Fukui Prefecture.

Hayashi is also charged with compelling Asano to strangle herself with a chain at his home in Gifu Prefecture. Asano died of suffocation, the indictment said.

Hayashi's defense counsel has accepted almost all the charges in the indictment, but said Asano killed herself "of her own will."

The prosecutors said Hayashi treated his girlfriend "like a slave," and his strong control over her meant she was left with no option but to strangle herself.

Defense lawyers have also argued that the defendant planned the murder with an accomplice, Tomoyuki Watanabe, 38, who is serving a 14-year prison sentence for the crime.

But Watanabe has testified that Hayashi alone planned the murder and he could not refuse to participate because he thought Hayashi would kill him.

The court is set to hand down its ruling on July 15.