An original story from director Baku Kinoshita and writer Kazuya Konomoto, this is the kind of quiet, contemplative anime feature that rarely gets a theatrical release. Enveloped in the dusk, the film opens in a lonely prison cell, home to the elderly former yakuza Akutsu. Now on his deathbed, he finds an unexpected confidant in … a talking balsam flower. (The legend goes that only newborns and the dying can converse with the plant.) Over the course of one sleepless night, his life story unfolds in bursts.

Thirty years prior, another balsam flower also grows in the back yard of Akutsu’s humble house, which he shares with Nana and her baby son, Kensuke. The relationship between the taciturn man and the bubbly young woman is seemingly platonic; Kensuke is not his son. Yet there are hints of romantic attraction; they share bowls of piping hot ramen noodles, play endless rounds of Reversi, and join in harmonising the Ben E King classic Stand By Me.

In contrast to this alternative nuclear family, the yakuza world is still strictly traditional, revolving around machismo and codes of brotherhood. When Kensuke is diagnosed with a heart condition, Akutsu is lured into a criminal plot, which leads to his incarceration. Though encompassing much bloodshed and even a hidden treasure subplot, The Last Blossom is most moving as an exploration of human conscience, where a capacity for violence and kindness coexist. The paradox is reminiscent of Shōhei Imamura’s Palme d’Or winner The Eel, starring Koji Yakusho as a wife-murderer who shelters a pregnant woman after his prison release. With his unassuming buzzcut, in stark contrast to his flamboyant yakuza peers, Akutsu bears a striking resemblance to Yakusho’s protagonist. Though a minor work compared to Imamura’s, The Last Blossom similarly questions conventional notions of justice, and the impossibility of weighing one’s good and bad deeds.

• The Last Blossom is in UK and Irish cinemas from 27 March, and in Australian cinemas from 23 April.