Arriving at the center of the nuclear industry
On walls, T-shirts, and the floor of the school basketball court at Richland High is a large, green letter R against a cartoon mushroom cloud.
It is a source of local pride that the town produced the plutonium for the bomb that was detonated over the city of Nagasaki in 1945. They say their work helped bring an end to World War 2.
"Proud of the cloud" is the school slogan. The high school sports teams are known as the Bombers.
Koga arrived at the school in August 2018 from her home prefecture of Fukuoka. At first, the local ideas about the bomb barely registered with her. But that changed one day in history class, when she heard for the first time an account very different to what she had learned back in Japan.
Later she talked about it with Shawn Murphy, a teacher she was close to, and he asked if she knew what the mushroom cloud on her hoodie actually was. When she couldn't answer, he explained that it was made of the buildings and people it destroyed.
"I felt so frustrated with myself," she says. "I'm Japanese but I didn't think very seriously about the logo. I also realized that most of the people around me were the same. They only knew the superficial facts about the cloud, but nothing about what was actually happening underneath."
"She was very shocked and she was actually in tears," says her teacher. "That's the day she decided to speak up and say something."
Playing her message
Koga was due to head back to Japan soon after that lesson, and Mr. Murphy offered her a platform to share her ideas. He suggested she appear in a video to play to the school. With the help of her host mother, she began working on a script.
She also took a tour of Richland's old nuclear reactor to learn more about the local history and why the residents were so proud of producing plutonium for the bomb.
On May 30th, Koga played the video for the entire school.
"Those who were bombed were civilians, not soldiers. Should we have pride in killing innocent people?" Koga asks in the video.
She also explained that the town her grandparents grew up in was the original target of the second atomic bomb, but clouds forced the bombers to go to plan B and hit Nagasaki instead.
Koga ended with the words, "I'm here today because it was a cloudy day."
The video's effect
Koga says she was so nervous the night before the video was screened that she couldn't sleep. She had no idea how people would react. In the event, the response from her close friends was overwhelmingly positive.
"She's brave, she's courageous, I'm very proud of her for stepping up and saying what she wanted to say," Mr. Murphy says.
Koga's video caught the attention of the local media, and it sparked a debate among the Richland residents over the rights and wrongs of the logo.
The school still has its mushroom cloud motif, but Koga says she was never asking them to remove it. She just wanted them to think about the 80,000 people represented by that graphic, and about how she owes her life to the other clouds that day.