前原真记和弟弟宏、父亲道夫三人一起生活。母亲多惠在 18 年前为了另一个男人弃家而去,但父亲从未吐露过一句对母亲的怨恨。道夫突然过世后,真记在电脑里写下自己的心情:“母亲,和那个人在一起,您过得幸福吗?父亲已经离去了,什么都没有说。”偶然的机会宏发现了这篇文章,瞒着真纪寄给了“日本最短的给母亲的信”作文大赛。宏也从此开独自寻找母亲,终于迎来和母亲的相逢…。"Mother, are you happy with him? Father said nothing and died quietly." Hiroshi borrows his sister Maki's laptop computer and finds a short message written to the mother who had abandoned them. Without telling Maki, Hiroshi submits her message to a Fukui prefecture collection, and it wins a prize. The episodic narrative gradually fills in the background to this message. She goes from being a design company employee to a restorer of medieval art works. He is a university student in Tokyo. Their father died of a heart attack and never spoke about the divorce from their mother. Hiroshi meets the mother and tries to bring her back to the family, despite Maki's violent objection.