In present-day Tokyo, 23-year-old Sawako Kimura (Hikari Mitsushima) is on her fifth part-time job and is dating her fifth boyfriend. Kenichi Arai (Masashi Endō) is a second-rate designer at the toy company where Sawako works and has a four-year-old daughter, Kayoko (Kira Aihara). Kenichi wants Sawako to marry him, but she thinks he's "just average" (she also thinks she's "nothing special") and she doesn't like children.
At the same time, Sawako's uncle Nobuo Kimura (Ryo Iwamatsu) keeps calling and asking her to return to her hometown because her father Tadao Kimura (Kotaro Shiga) is dying of liver cirrhosis. The uncle wants Sawako to take over her father's freshwater clams packing business, which is in financial difficulties. When Kenichi is fired from his job as a toy designer, he persuades the reluctant Sawako to accept the offer to return home and take him and Kayoko with him. After 1,100 km by train, the trio arrives in the Pacific coast town of Kawaminami in southern Japan. There, Sawako is despised by the women because she ran away from home to Tokyo with her high school tennis club captain Yoshio (Ryu Morioka) five years earlier.
The moment comes when Sawako has to decide what she wants to do with the freshwater mussel packing company, her boyfriend Kenichi and his daughter Kayoko and her whole life.