During 40 months of captivity by Syrian militants, Japanese journalist Jumpei Yasuda says he was forbidden from moving or making noise.
Guards told him daily he would be released, and sometimes gave him canned food but no opener, he said.
Mr Yasuda was released earlier this week and has now arrived home in Japan.
He has given the first details of his three years in captivity, which he called physical and psychological "hell".
He told the Asahi Shimbun Daily that his captors accused him of being a spy.
Confined for eight months to a space just 1.5m high and 1m wide, he was not allowed to bathe, wash his clothes, or make any kind of noise or movement.
"Because I couldn't wash my hair, my head itched - but when I scratched, that made noise," he told the Asahi during his flight back to Japan.
"Breathing through my nose, cracking my knuckles, moving while I slept - everything was forbidden."
At one point, he didn't eat for 20 days in an effort to avoid any movement.
"I was skin and bones, horribly nauseated. If it had gone on much longer, I would probably have died, but I was finally moved to a different place," he said.
"They would not bring me food, or if they did give me canned food, they would not bring a can opener," he said.
A week before his release, he was moved back to the narrow space of his worst days, then to a cell in what appeared to be an ordinary house.
The following day, he was put in a car and driven to the Turkish border.
Gaunt and bearded, wearing a black T-shirt and dark trousers, Mr Yasuda gave reporters a strained smile upon his arrival in Japan, but said nothing.
His wife told a news conference that any further comments would have to wait until he had rested and undergone medical checks.
"I'm happy that I can return to Japan.
"At the same time, I don't know what will happen from here or what I should do," Mr Yasuda told Reuters on a Turkish domestic flight, before he flew home from Istanbul.
The Japanese government has thanked Qatar and Turkey for their cooperation in freeing Mr Yasuda, but has denied paying a ransom for his release.
Mr Yasuda was kidnapped in 2015 by al Qaeda's branch in Syria, known at the time as Nusra Front, after his contact was lost in June that year.
A war monitoring group said he was most recently held by a Syrian commander with the Turkistan Islamic Party, which mostly comprises Chinese jihadis in Syria.