Nagi seems to have it all: a good job, a boyfriend, friends at work. Unfortunately, she overhears her coworkers and boyfriend dissing her, so she stays home from work, and no one comes to see her. She decides to quit, and move to the country, and let her curly hair hang free.

Yukari Kawahara works at a drink manufacturer. She works hard and achieves recognition for her work. Yukari Kawahara is dating research doctor Kippei Koide. They have lived together for 5 years. One day, Kippei Koide collapses from a brain hemorrhage. Yukari Kawahara soon learns that everything she knew about her boyfriend was a lie. She hires private detective Takumi Kaibara to investigate Kippei Koide.

匆忙浮躁的都市中，四个与音乐相关的男男女女看似偶然般地邂逅了，他们分别是第一小提琴手卷真纪（松隆子 饰）、大提琴手世吹雀（满岛光 饰）、中提琴手家森谕高（高桥一生 饰）以及第二提琴手别府司（松田龙平 饰）。仿佛是对音乐的共同志向，他们组建了名为“甜甜圈洞”的四重奏乐队，暂时落脚于别府家位于轻井泽的别墅，过起了与世隔绝的人生。然而四个人终究无法超脱世俗存在，除了最基本的吃饭问题，每个人似乎都被各自的秘密所牵扯纠缠。其中雀与真纪“邂逅”的原因，恰恰正是因为真纪丈夫的不辞而别。
雪花飘落，寒风萧瑟，四重奏的悠扬旋律荡涤且治愈着他们每一个人的心……