The Masked Ball

The characters in the story are:

Jungwon - a friend of Y/n who is also an international spy
Jay - another friend of Y/n who is also an international spy
Y/n - the protagonist of the story who attends a masked ball and becomes involved in a spy mission
Niki - a spy from the Russian government
Heeseung - a spy from the South Korean intelligence agency
Jake - a spy from the British Secret Intelligence Service
Sunghoon - a spy from the CIA
Sunoo - a spy from the Israeli Mossad

The story follows Y/n as she attends a masked ball and becomes involved in a spy mission with her friends Jungwon and Jay. She discovers that they are international spies and they are on a mission to retrieve a valuable diamond necklace. However, she later finds out that the other guests at the ball are also spies, and they are all competing to retrieve the same necklace. In the end, it turns out that the necklace is a fake and the whole event was a test to see which spy organization was the most skilled. Y/n and the other spies pass the test, and the leader of the spy organization offers them a job as full-time spies.