Heat a medium saucepan over medium heat. One hot, swirl in some sesame oil and add the onion. Stir to coat. Add the ginger.
Once the onion has softened and is starting to brown, add a cup of water. Add the miso and stir it around with a wooden spoon--it's okay if it doesn't dissolve all the way. Cover and bring to a simmer. Add the entire can of corn, including the juice. Stir and cover again to bring to a simmer.
Lastly, turn down the heat. Whisk the eggs in a separate bowl until smooth, then pour into the soup. Immediately stir the soup in a clockwise motion to disperse the egg evenly throughout the soup. Finish with a dash of soy sauce if desired.