In a futuristic city where everyone has a "personal sound", a sound frequency that is only heard when they enter a new room, a rare glitch occurs: a young woman discovers that her personal sound has been replaced by a sound that belongs to another person, a complete stranger. At the same time, that stranger discovers that he has completely lost his sound, and is moving in "total silence", which is considered dangerous and illegal, because society is based on unique voice recognition instead of ID cards. The two are forced to meet to understand what caused the disruption, but as they get closer, their sounds merge and create a new melody that does not exist in the system. This melody is capable of opening secret doors in the city that have not been opened for centuries, which arouses suspicion from both the authorities and underground groups who want to exploit the new power.