Japanese Ministry of Foreign affairs diplomat Kosaku Kuroda (Yuji Oda) is dispatched all over the world to protect Japanese interests and citizens.After successfully defeating a kidnapping attempt of Japanese citizen in South America, Kuroda is assigned to protect Foreign Ministry official Shoko Mikami (Tamiyo Kusakari) in San Francisco during a World Trade Organization meeting. He meets informant John (Lee Byung-Hun) who gives details on security arrangements and former diplomat Takeshi Shimomura (Teruyuki Kagawa) who worked with Kuroda at the Mexican Embassy 11 years ago.With the help of the information received from John, diplomat Kosaku Koroda is able to prevent an attack on Shoko Mikami by extremists, but as he investigates how the attacker knew of Mikami's movements, Takeshi Shimomura jumps off a building to his death.Meanwhile, a suspect emerges in the murder of a university professor in Japan that took place recently.

爆款悬疑作家芹泽环坠梯身亡的震撼新闻过去一年后，本应终于能成为其新作责编的江藤惠，从妻子真理子处听闻有芹泽未发表手稿，遂拜访其家。她在那里发现的，是芹泽遗留的“日记”。找到因意外猝逝的芹泽生前思绪的宝藏，江藤在愧疚感中怀抱亢奋。然而阅读之中，虽内容看似真实，却总觉得与自己所知的“芹泽环”有所不同。“这，究竟是谁写的？”。
另一边，真理子在芹泽死后，得知他只向生成式AI倾吐烦恼。她在芹泽遗留的日记中，基于与AI对话所得要素进行创作性增补，并展示给江藤。
江藤一直无意识受困于芹泽曾说“人生的重要一页是何时？若对你而言就是现在，我乐意创作新作”的言语。以此日记为契机，“想要赶上人生机遇”的欲望膨胀。“创作方能传递真实”，芹泽也曾如是说。江藤向真理子提议，将日记构思延续至事故身亡前夕。真理子为深入理解芹泽行为而深化与AI对话，在执笔日记过程中，竟奇妙地陷入较丈夫生前更似与之交谈的错觉。二人一面面对芹泽的思绪与各自的过往，一面试图以芹泽环之名将这份“日记”公之于世。然而，渴望了解创作众多名作的爆款作家内心世界的，并非仅此二人。江藤与真理子的过错，将引发超乎预想的混沌―。