It seems that this is the song whistled by the psycho killer Jung hyun Soo in “Suspicious partner”
https://youtu.be/hin_rIgiuUM
On another website, someone (probably a Korean) nicknamed Chicken Feet, offered the following explanation.
[QUOTE]
This is theme song of a korea drama, adapted from korean classic novel:
A sonagi is a brief but heavy rain shower that starts suddenly, usually on a hot afternoon. In Hwang’s story, the rain shower symbolizes the short but heart-rending love between the boy and the girl. The story begins with the boy encountering the girl playing by the stream on his way back home.
Although many of Hwang’s short stories are notable, “Rain Shower” is cited as his timeless Korean classic by Koreans. Koreans of all ages are acquainted with this story. It is famous for its poignant depiction of the Korean countryside and of innocent adolescent love. The picturesque scenes from this story stir nostalgia for many people.
“Rain Shower,” like many of Hwang’s other stories, was written while he lived as a refugee with his family during the Korean War.
The scene from the story where the boy and the girl avoid the rain shower together has become a favorite in many Korean romantic films. There is a 1979 Korean film based on the short story (also called Sonagi). Two notable films that heavily reference the story include the 2001 Korean romantic comedy, My Sassy Girl, and the 2003 Korean melodrama,
LYRICS:
I’ve got a grass leaf.
I also put pretty blossoms on it.
When you shine in the light of the sun
Put a pretty flower hat and give a wave
I took off the rubber on the stream.
To soak in the flowing stream
When will she cross the bridge?
My breasts were two.
On a flowing stream
The glow is pinkish
Between the clouds
The evening is shining.
On a gleaming stream
Pretty flower hat floating
One of the little boys’ sad love stories
A grass leaf was weaved.
I also put pretty blossoms on it.
When you shine in the light of the sun
Put a pretty flower hat and give a wave
I took off the rubber on the stream.
To soak in the flowing stream
When will she cross the bridge?
My breasts were two.
On a flowing stream
The glow is pinkish
Between the clouds
The evening is shining.
On a gleaming stream
Pretty flower hat floating
One of the little boys’ sad love stories
On a gleaming stream
Pretty flower hat floating
One of the little boys’ sad love stories [/QUOTE]
And there is another video, taken from a film