Militants from the Islamic State group released a video purportedly showing the beheading of Kenji Goto, one of the two Japanese hostages the jihadists were holding.
Last week, IS claimed responsibility for the beheading of self-described contractor Haruna Yukawa in a separate video.
The pair were friends and travelled at least once together in the Middle East. Goto went to Syria to help find the captured Yukawa, and was taken hostage himself late last year.
Here are brief profiles of the men.
Goto, 47, is a freelance journalist who established a video production company, Independent Press, in Tokyo in 1996, supplying documentaries on the Middle East and other regions to Japanese television networks, including public broadcaster NHK.
Goto had apparently been out of contact since late October after telling family that he intended to return to Japan, NHK reported.
In early November, his wife received email demands for about one billion yen ($8.5 million) in ransom from a person claiming to be a member of Islamic State, Fuji TV said.
The emailed threats were later confirmed to have come from a sender implicated in the killing of US journalist James Foley, Fuji TV said.
In video footage he filmed around the time he entered Syria, Goto holds identification papers and his Japanese passport and explains that he is aware of the risks.
"Whatever happens, I am the one who is responsible," he says. "I am asking you, Japanese people, do not place responsibility on the people of Syria. Please. I am sure I will come back alive, though."
Goto's mother later pleaded with the hostage takers to release her son, whom she described as a humanitarian working to better the lives of children.
"I say to you people of the Islamic State, Kenji is not your enemy," a sobbing Junko Ishida told foreign journalists.
"Please release him... Kenji was always saying 'I hope to save lives of children on battlefields'. He was reporting war from a neutral position."
Goto's wife Rinko broke her silence this week to plead for her husband's return.
"My husband is a good and honest man who went to Syria to show the plight of those who suffer," she said.
The couple had a second child several weeks before Goto left for Syria.
He was born in Sendai, Miyagi, in 1967, according to the company's website.
Yukawa is a 42-year-old widower who reportedly has a history of attempted suicide and self-mutilation.
He opened a military goods shop in Chiba, outside Tokyo, after leaving high school, according to a website affiliated with the popular Sankei newspaper.
He married in 2000, but his business soon went bankrupt and his wife later died of cancer, the website has said.
Citing his father, the website said a devastated Yukawa changed his original name -- Masayuki -- to Haruna, usually a woman's name, in the belief that the Chinese characters used would herald a shorter life.
The website said he had tried to kill himself and had cut off his own genitals.
Yukawa came to widespread attention in Japan when footage of his apparent interrogation in the Syrian scrub was posted online last August.
He was seen lying on the ground, with matted brown hair and wearing a black T-shirt stained by dust and sweat, as blood trickled down his face.
Yukawa offered brief responses to questions posed in English about why he was in Syria and the reason he was carrying a gun.
He replied in stilted English that he was a "photographer" and a "journalist, half doctor", as his interrogators accused him of lying, with one placing a long knife near his chest.
"I'm no soldier," he said.
Another video surfaced showing a man believed to be Yukawa test-firing an AK-47 assault rifle in Syria.
The same video could also be seen at the website of Tokyo-based private military firm PMC, which lists Yukawa as its chief executive. Pictures on the website show him with right-wing Japanese activists.
Its website said the firm has branch offices in "Syria, Turkey, Iraq, Africa", and it says its services include providing "security abroad".