Tsutomu (Sawada Kenji) is a writer who lives in a secluded mountain cabin in Nagano. He shares the space with his dog and the unburied ashes of his wife Yaeko, who passed away thirteen years ago, and spends his time harvesting vegetables, then cooking with them using a method he learned as a young Buddhist monk. Though largely solitary, he receives occasional company from his editor and romantic interest Machiko (Matsu Takako), and from his rather eccentric mother-in-law, Chie (Naraoka Tomoko).

When Tsutomu one day finds Chie dead in her home, he is forced to finally consider his feelings on death. He works to arrange Chie’s funeral proceedings, and once the funeral has concluded, invites Machiko to live with him, an offer to which she gives serious thought.

Based on an essay on food and cooking by leading Japanese author Mizukami Tsutomu, The Zen Diary eschews drama in favour of its focus on zen cuisine and seasonal scenery, offering audiences a glimpse into the joys of a slow, simple life seen through the lenses of bonds, memory, and love.