With her black bob hair, large glasses that hide her face, and a clumsy suit, Mari Hatanaka, a plain office lady with a secret, is nicknamed "the Iron Mask of the Accounting Department" at work because of her expressionless face and cold tone. One day, a bowl of curry udon noodles flies through the air, and that's when she begins to interact with Yuzuru Takanashi, the "Prince of the Sales Department." Having been the victim of a stalker in the past, Mari tries to keep a low profile, but she is spotted by a colleague at work with Yuzuru. As she is criticized by women, she has flashbacks to past trauma, but Yuzuru reaches out to Mari, who endures the situation alone, saying, "Let me protect you," and Mari ends up staying at Yuzuru's house until the problem is resolved...! This is a doting love story that begins with a plain office lady with a secret and an elite salesman living together.