After a year in America, Kurisu Makise returns to Akihabara and reunites with Rintarou Okabe. However, their reunion is cut short when Okabe begins to experience recurring flashes of other timelines as the consequences of his time traveling start to manifest. These side effects eventually culminate in Okabe suddenly vanishing from the world, and only the startled Kurisu has any memory of his existence. In the midst of despair, Kurisu is faced with a truly arduous choice that will test both her duty as a scientist and her loyalty as a friend: follow Okabe's advice and stay away from traveling through time to avoid the potential consequences it may have on the world lines, or ignore it to rescue the person that she cherishes most. Regardless of her decision, the path she chooses is one that will affect the past, the present, and the future. The film takes place one year after the events of the anime series. After going through a painstaking journey across multiple World Lines due to the invention of D-Mail, text messages that can be sent to the past, Okabe Rintarou has assumedly landed in the Steins Gate World Line, in which none of his friends would have to die and a future ruled by SERN due to the invention of a time machine no longer exists. However, Rintarou soon starts feeling the side effects of his constant time travelling across multiple World Lines, which soon builds up and causes Rintarou to suddenly vanish from existence, with only Makise Kurisu, the girl who he had saved thanks to his efforts, remembering him through déjà vu. It is now up to Kurisu to find a way to get Rintarou back.