Nagisa Oshima is an important Japanese director and this was a personal project of his. It wasn't intended for commercial screening and it has an eccentric format and duration... but it reached cinemas anyway. It's pretty shocking.
First, some history. Japan conquered Korea in 1910 and ruled it harshly until 1945, whereupon (like Germany) the country was split into a communist half (the North) and a Western-oriented half (the South). It's still like that today. North Korea is a sinister basket case that's only survived thanks to decades of support from the Soviet Union and China. The Korean War (1950-53) was the North invading the South and achieving only 3 million dead and both economies in ruins.
Mind you, even South Korea was a nasty authoritarian state for many years. This film mentions the 1960 demonstrations that preceded the May 16 coup of 1961, but it wasn't until 1987 that the military regimes ended and South Korea became a proper democracy.
Anyway, Oshima visited Korea in 1964 and was shocked. This film is the narrated diary of a ten-year-old boy, accompanied by black-and-white photos taken by Oshima himself. Yubogi lives on the streets. His mother's disappeared and his father's ill. He roams the streets, selling gum or shining shoes to earn tiny amounts of money and try to keep himself and his three siblings alive. The photos make it shocking. It's a documentary. It's real. Oshima's simply showing us what he saw, with the narration bringing it alive. There's no happy ending. We never learn what happened to Yubogi's mother and he'll never know either.
In fairness, this film isn't portraying the direct actions of Japan. Yunbogi was born a decade after Japan left and we're seeing life under the (Western-backed) South Korean regime. Observe the 23:30 curfew, for instance, and the "bark like a dog" way of avoiding arrest. Children are starving, probably sometimes to death. Nonetheless, Japan's occupation didn't help, while right-wing Japanese politicians even today deny or downplay things like Japanese massacres of Korean civilians or the kidnapping of girls aged 12-17 into sex slavery (known as "comfort women"). On the other hand, this film pulls no punches. It strongly implies that we're seeing the fruits of Japan's oppressive 35-year regime, with Japan's treatment of Koreans being a subject Oshima returned to in films like Sing a Song of Sex (1967), Three Resurrected Drunkards (1968) and Death By Hanging (1968).
If you watch this film, you won't forget it.