In a first-hand account in a South-Korean magazine,the Australian also said he was"kidnapped"from his dorm at the university by secret police.
Alek Sigley has commented for the first time since he was accused by North Korea of being a spy.
Experts said it was impossible the North Korean regime had not been fully aware of Mr Sigley's activities since the moment he arrived in the tightly restricted nation.
An Australian student who was released by North Korea after being detained for a week had spread anti-Pyongyang propaganda and engaged in espionage by providing photos and other materials to news outlets with critical views toward the North,North Korea has alleged.
He might be willing to go back to North Korea and resume his education travel business.
Diplomats remain tight-lipped about the reason for Australian student Alek Sigley's detention. But a theory emerging is that he was simply being silenced.
Sigley,who flew to Tokyo on Thursday to join his Japanese wife,had been studying in the North Korean capital and had been missing since June 25.
When Kent Harstedt landed in Pyongyang on Monday,authorities wouldn't even admit they had an Australian in custody. A delicate diplomatic dance began.
Alek Sigley walked past waiting reporters without any comment after arriving in Japan from Beijing. He was released from North Korea after Sweden intervened.
Alek Sigley will travel to Tokyo after Swedish officials helped secure his release by making representations on Australia's behalf.
Alek Sigley’s father Gary spoke to media on Thursday afternoon in the wake of news the 29-year-old had been released by the North Korean government and was en route to Japan.