影片讲述一名平凡的主妇收到一封来自美容师的邮件，因此为契机主妇化作一名跟踪者而引发了一系列故事。主妇小夜子由常盘贵子饰演，美容师海斗则由池松壮亮担当。另外，小夜子的丈夫光太郎由胜村政信出演，海斗的恋人唯则是佐津川爱美担任。 《谁的木琴》的主题是在人类之间的联系逐渐变淡的现代，女性在精神上的饥饿感、疏离感以及不得不和其对峙的男性之间所产生的共鸣。

War photojournalist Yasuyuki Tsukahara married popular manga artist Yuki Sonoda and had children. Because of Yasayuki's drinking problems the couple divorced. Yasuyuki is now coughing up blood, hospitalized, and violent. Even with all of these problems Yasuyuki can't give up drinking alcohol. His family gets tired. Yasuyuki is then hospitalized in an alcoholic ward. There he finds comfort living with other patients and having conversations with doctors. With the help of his family, Yasuyuki recovers mentally and physically, but his body has already paid a heavy toll.

A young woman breaks off her long-term relationship with her boyfriend to move to Tokyo in search of new experiences.

Mariko is living the life of a typical Japanese college student in the 70's, spending far more of her time balancing boyfriends and part-time jobs than on her schoolwork. She finds herself torn between a former boyfriend who's the tough, insensitive-but-sexy, type, and a new acquaintance who's more sensitive to her feelings, but who still acts childishly selfish at times. Will she choose one of them, or decide to go her own way?