坐落于五岛列岛福江岛上的五岛中学，由于合唱团指导老师松原晴子（木村文乃 饰）待产休假，她便委托好友柏木由里（新垣结衣 饰）代课一学期。柏木美艳冷漠，学生们对她既好奇又忌惮，虽然听说她曾是某交响乐团的钢琴家，可是却因某种原因而辞职回家，并且决然不愿指导学生们练习。女神般的老师从天而降，吸引一帮原来对何尝没有任何兴趣的男孩加入这个清一色的女生团体中来。而女孩子们与男孩争吵不断，她们也对柏木老师的不闻不问颇有微词。一年一度的NHK全国学校音乐比赛即将召开，合唱团积极练习指定曲目《信～敬启　致十五岁的你～》。在此期间，柏木老师深藏心底的秘密逐渐浮出水面，而孩子们也在音乐的熏陶中找到人生的方向…… 　　本片根据作家中田永一（乙一）的同名小说改编（又译《再会吧，青春小鸟》）。Yuri Kashiwaga was once known as a genius pianist. One day, she returns to her hometown in Goto Islands from Tokyo. There, she begins to work as a temporary teacher at a middle school and advisor for the school chorus. The chorus aims to take part at a competition. Yuri gives the members of the chorus members an assignment. She instructs them to write a letter with the title of "To myself 15 years later." The 15-year-old boys and girls write about their secrets and worries.