海乃环（广末凉子 饰）是FM广播电台午夜节目的栏目策划人，由于无人收听，她的节目面临停播的命运。沮丧的她听到Candies乐队的老歌《比我小的男生》，思绪飘回1977年。 　　1977年的棒球赛场上，高野太郎（神木隆之介 饰）一边模拟着棒球场播音员的赛事直播一边奋力发球。 高野太郎是电台节目《音乐快车》的忠实fans，每日一边收听一边练球。这天突然在学校晕倒，没过多久进住进了医院，乏味的生活和无休止的抽血检查让太郎消沉，直到偶然闯入大医生的房间，当起了小DJ，每日中午为医院病人播放歌曲。 　　小小DJ生涯彻底改变了太郎的住院生活和人生，也改变了他身边的病人和医护人员，因车祸住院的海乃环（福田麻由子 饰）就是其中之一，这个总是爱甜甜微笑的小女生总爱陪在太郎身边。太郎想对她表白却总也开不了口，他写下一封点播信给最信任的《音乐快车》的DJ，信还未寄出，太郎的生命已经迅速衰弱下去。

Taro is a 12-year-old into baseball and radio, especially "Music Express," a song-request show. Sound quaint? But it is 1977 and a small town in Hokkaido, a more innocent, pure-hearted time and place, we are told. Taro, however, has a blood disease that lands him in the hospital where his aunt is a nurse. Rounds of tests, transfusions and injections sap his spirit, despite the kindness and dedication of his young doctor and the Doctor's hospital-director father. The latter, a music buff who broadcasts classics over the hospital's PA system, asks Taro to relieve him as DJ — and soon the boy is ensconced in the hospital director's well-stocked library-cum-studio, spinning popular J-Pop tunes. He also becomes acquainted with Tamaki, a girl he first calls "the mummy" because of her bandages and full body cast — she was injured in a traffic accident. He later changes his tune when she is revealed as a cute 13-year-old — for him, an older woman...

타마키는 신청곡이나 사연이 담긴 엽서 한 장 오지 않는 심야 프로그램 라디오 PD이다. 덕분에 청취율의 문제로 프로그램이 개편되며 1달간 휴가를 가지게 된다. 지친 타마키는 우연히 자기를 라디오 PD로 만들어 준 작은 소년의 추억을 떠올린다. 타마키가 불의의 사고로 병원을 찾게 되던 중학교 2학년의 여름, 병원 내 점심 방송을 담당하는 모든 사람들을 행복하게 해주던 DJ 타로. 덕분에 타마키 역시 힘든 병원 생활을 이겨나가게 되며 타로와 타마키는 아름다운 추억을 만들어 가는데..