同上一所高中的木岛朔（野村周平 饰）、城崎修太（福士苍汰 饰）和俏皮可爱的安藤美知留（本田翼 饰）是从小形影不离、知根知底的好朋友。某天，美知留托修太将一封信转交给朔，随后竟然不辞而别，只身前往英国留学。而朔则在看信后狂奔到车站，导致旧病复发，遽然离去。这一事件令此前偶然借走朔自行车的修太分外自责，在好友第三年的忌日上，他偶然找到一只据说可以穿越时空的手表。带着对两位好友深深的思念，修太竟然真的回到了三年前。也许是上天的眷顾，让修太看到了改变好友命运的机会。 少男少女未曾说出的话语，残酷的青春命运，可否因此发生变化？

新一年的学生会选举即将来开序幕，绯樱山中学逐渐为热烈而紧张的气氛所感染。在国语教师铃木章（长谷川博己 饰）的鼓励下，学生们纷纷勇敢站出，积极投身选举之中。铃木为此欣慰不已，只不过在照顾怀孕的妻子麻美（臼田麻美 饰）的同时，还不得不与心中针对爱徒小川苏美（土屋太凤 饰）的邪念作斗争。在此关键时刻，与铃木老师截然对立的足子瞳（富田靖子 饰）强势回归，大力推行全员有效投票的选举制度，而一向蔑视选举的出水正则高调参选，使得此次选举充满变数。另一方面，八年前毕业于绯樱山的胜野（风间俊介 饰）经历了社会最残酷的现实，满怀怨恨重返校园，引起莫大的骚动…… 本片根据漫画家武富健治的同名原作改编，为该电视剧的电影版

At a high school entrance ceremony, high school student Kotoko Aihara (Honoka Miki), who isn't that smart, notices pretty boy Naoki Irie (Yuki Furukawa). She falls in love with him immediately. Kotoko initially doesn't express her feelings to him, but finally has a chance to tell him how she feels. Unfortunately, Naoki turns Kotoko down, saying "I don't like dumb women." One day, Kotoko Aihara's house is severely damaged by an earthquake. Until the house is rebuilt, Kotoko Aihara and her father decide to live with her father's friend. When Kotoko Aihara moves to her new temporary house, she is surprised to learn that Naoki Irie lives there as well.