A lot of eating goes on in the new documentary "Gokutomo" ("Friends in Prison"), which is about five men, all convicted of murder, who spent many years in prison. Watching one of them casually buy a sweet bean bun at a convenience store, you realize that, as an indulgence, food can be the most obvious marker of freedom. Locked up for decades for crimes they say they didn't commit, these men appreciate the relative luxury of being able to eat any time they want to.

The director, Kim Sung-woong, began filming in 2010 as a means of finding out how one of the men, Kazuo Ishikawa, who spent more than 30 years in prison for allegedly killing a high school girl in 1963 before being paroled in 1994, was adjusting to life on the outside. At the time, Ishikawa had asked for a retrial to prove his innocence. (Now 79, he is still trying to get a retrial.)

Kim learned that Ishikawa befriended four other men in Chiba Prison who claimed they were wrongly convicted of murder, including two on death row. In 2011, two of the men, Takao Sugiyama and Shoji Sakurai, were acquitted of the same 1967 robbery-murders in a retrial. Similarly, Toshikazu Sugaya was acquitted in 2010 of the 1990 murder of a little girl after serving 17 years of a life sentence. The fifth member of this select club and oldest is 81-year-old Iwao Hakamada, who was convicted in 1966 of killing a family. Out on provisional release since 2014, Hakamada is technically still on death row as he waits for his own retrial.