Hay’at Tahrir al-Sham declared its affiliation with Al Qaeda in 2013, but says it is no longer connected. The State Department declared it a terrorist group in 2012 and renewed the designation this year.

In July, Japanese television stations broadcast a video in which Mr. Yasuda spoke to the camera against a black backdrop.

“I hope all of my family is fine,” Mr. Yasuda said in the video. “I want to see you.”

Before that, he had last been seen in a video in 2016, followed by a photograph two months later that showed him holding a handwritten note that reads in Japanese: “Please help. This is the last chance.”

Mr. Yasuda had been a hostage before. In 2004, he spent three days in captivity when he and several Japanese citizens were captured in Iraq, but they were not welcomed warmly upon their return. Critics said they were “Japan’s shame” who had “caused trouble” for everybody, and the government said it would bill them for their airfare.

He said at the time that the stress of his return was greater than the stress of his captivity. He had quit his job at a regional newspaper to report from Iraq.

“We have to check ourselves what the Japanese government is doing in Iraq,” Mr. Yasuda said in 2004. “This is the responsibility on the part of Japanese citizens, but it seems as if people are leaving everything up to the government.”

Mr. Yasuda’s mother, Sachiko Yasuda, said Wednesday on NHK that she had folded nearly 10,000 paper origami cranes since he went missing, making at least one every day.

“I couldn’t stand without doing anything,” she said. “I kept folding the cranes, praying for his safety.”