"You heard that voice earlier, didn't you...?"

Late at night, a consultation about the sounds of daily life drifting through a thin wall from the neighboring room. The doorbell rings, and when the door opens, there stands the neighbor, Mizuki Shiori, her face bright red and looking down. "Um... you heard it, didn't you...?" The quiet and reserved girl's anxieties and worries. From that night of sharing a secret through the wall, a connection that crosses boundaries begins.