Hong Tae-yi had a heated argument with Shin Yi-ru, her contentious team member from the same group project. Later, she discovers a mysterious app on her phone and unexpectedly encounters Shin Yi-ru again at a drinking party. To her surprise, she notices a peculiar number floating above his head. Unbeknownst to her, Hong Tae-yi has unwittingly triggered a strange phenomenon. "I'm not sure what's happening yet... Can you elaborate a bit more?"