I'm not a Buddhist, but I think I'm safe in saying this is a Buddhist film. There are few characters, but a couple of the main ones are monks or monks in training. But it's not the narrative that is Buddhist, as much as it is the setting, the pace, the spiritual nature of the film. Most of Spring, Summer, Fall, Winter ... and Spring takes place in a monastery that sits in the middle of a lake. It is never explained how the floating monastery got there, or even how it floats. On the other side of the lake are large doors through which the camera, and at times the characters, move. But the doors don't serve a concrete purpose ... anyone could just walk around them. In a similar fashion, while the monastery only has one room, there is a door that people go through, even though they, too, could walk around them. There is something respectful about how these doors are treated. It is also part of the overall reality of the movie ... nothing is "real" at all on some level, but it doesn't play as fantasy. It's just a visualization of the spiritual. #938 on the They Shoot Pictures, Don't They list of the top 1000 films of all time (#173 on the 21st-century list).
At the beginning, we meet a monk and his young apprentice. With the passage of each season into another, time moves forward and the apprentice ages, from teenager to adult to middle age. Finally, he takes on his own apprentice. Kim manages to create a calm film, thanks to the pacing, the beauty of the imagery, and the musical score. It's not that "nothing happens", or even that only "nice" things happen. A broad spectrum of human behavior is seen in the film. The calmness comes from the acceptance that everything is one. Or not ... like I say, I'm not a Buddhist.