该片根据乾绿郎的小说《完美的蛇颈龙之日》改编。讲述了一位女子自杀未遂变成植物人后，男友通过医疗设备进入她大脑，并由此踏上了现实与虚幻的奇妙之旅。

某公司年轻社长天野（柄本佑 饰）在下属（森下じんせい 饰）的陪同下视察某港湾基地，他的父亲早就有吞并该港湾的雄心，如今随着“美丽新湾计划”的启动，天野的公司积极备战，势在必得。只不过这位新任社长显然缺乏干劲，虽然被下属誉为处在公司中央位置的最大最重要的齿轮，但他也没有任何的自豪感。视察当天，天野的注意力被一个名叫古川高子（三田真央 饰）所吸引。此后的日子里，他时常借故跑出公司，来到港湾工地，试图接近高子赢得对方的好感。他自以为是、自高自大的做法引来高子的不快，而天野的突然之举也引发了连番的混乱……

Provincial lord of the Arioka Castle, Murashige Araki, rebels against tyrannical despot Oda Nobunaga, and makes a stand at his stronghold castle. He decides to take siege but is subsequently surrounded by Oda's forces, leaving its denizens isolated and in need of allies. With the sensitive support of his wife Chiyoho, Murashige struggles to keep his hot-blooded retainers in check, while also protecting the castle and its people. One day, a young samurai is murdered within the fortress with the mysterious killer unknown. A succession of bizarre incidents follows. The suspects are Murashige's close retainers and the people inside the Arioka Castle's land. Outside, enemy troops lie in wait. Inside, traitors lie to conceal themselves. As suspicion runs rampant, Murashige seeks the help of a prisoner in his dungeon—dangerous master tactician Kanbei Kuroda—to solve the mysteries.