I stalk through Tokyo in search of chance encounters.

Photographing people in the street—instinctively and on the fly—is a full-time challenge. Each person you photograph is sensitive to the minute shifts in emotion and aesthetics around them.

We’re all involved in the same comedy, but there’s a moment when my subjects start to perform, when they become a particularly potent actor. Amusement, hate, pity, gravity—these feelings send a signal, like an electric pulse, that makes me press the button. It’s that snapshot, that moment of spontaneity, that you have to catch.

I’m sure that every person on the street has a story. And yet unless I am moved myself by what I see, my viewer will not be moved to look at my photo. This is always on my mind when I am shooting.

I am trying to make a photograph that captures the statement “once you see my photo, you never forget it.” That is the type of photo I wish to leave behind.

—Chulsu Kim

Our 2017 Street Photography Awards are now open for entries! Submit your work now for exposure to editors from National Geographic, The Guardian, TIME, and more. Learn more about the competition on its Call for Entries.