Hyun-sook (Kim Hee-ae) raises her two daughters, Man-ji (Go Ji-sung) and Cheon-ji (Kim Hyang-ki), with the meager income from working in a supermarket. Although the two girls are sisters, they have completely opposite personalities. Man-ji is withdrawn and rebellious, and has a very cold relationship with her family; Cheon-ji is cute and well-behaved, and often thinks of ways to make her mother happy. What Hyun-sook and Man-ji didn't expect was that the optimistic and cheerful Cheon-ji actually chose to end her life one day. This bad news hit Hyun-sook's family like a thunderbolt, making their already hard life even more difficult. However, even so, Hyun-sook and Man-ji still maintain a normal life. By chance, Man-ji accidentally learned some information about her sister's life, which made her understand the real cause of her sister's death and a secret she tried hard to hide.