July 28, 2010. Akihabara.
Within the bustling electronics district of Tokyo, a man with brushed-back hair and dressed in a lab coat takes a girl to a press conference. The man, named Rintaro Okabe, explains to his childhood friend Mayuri Shiina about the press conference at Radio Hall, which is about "The Invention of The Century": a Time Machine.
Suddenly, Rintaro's thoughts are disturbed by what he thought was an earthquake. Upon closer inspection, he finds a strange object on the roof. Soon, however, he is called back by Mayuri, who wants to take him to somewhere more interesting.
Mayuri is in front of vending machines. She laments on lacking 100-yen coins to play. What appears more unfortunate for her is that her childhood friend plans to waste his 100-yen coin on a blind spin on the vending machine. Ironically, Rintaro gets the rarest of the items available and, since he is not interested on the stuff he got, he gives it to Mayuri. The item she got is the Metal Upa toy figure in which she puts her name on it.
Soon, an announcement of the start of the conference is broadcast, and Mayuri and Rintaro part ways for the meantime.
The conference later begins, led by a certain Dr. Nakabachi. Rintaro attends the meeting, while Mayuri stays outside; Mayuri later tells Rintaro that she lost her newly-acquired Metal Upa toy figure and is looking for it. Rintaro soon continues on listening to the lecture, however, he finds out that there is something alarming about Dr. Nakabachi's theories on a time machine, which he describes as something pulled straight from the John Titor theory. This left Nakabachi angry and annoyed at Rintaro.
Before Rintaro could make any more fuss in the conference, he is pulled away by a young woman. At first, Rintaro complains about what she just did, but the young woman turns out to be Kurisu Makise, a famous figure in the field of scientific research. Rintaro resorts to his cell phone, in which he reports to "someone" regarding being caught by an operative of a certain Agency.
Kurisu manages to snatch his cell phone and discovers that it is turned off.
Rintaro tries to keep himself from being humiliated by the woman to no avail. Kurisu, however, goes straight into the topic, asking him about what he wanted to tell her fifteen minutes earlier. In response, Rintaro just gives a farewell remark and sprints downstairs.
For a moment, Rintaro feels nervous, still denying the fact that they have met before.
Soon, he receives a message on his phone, but instead of seeing a message, he finds a video displaying static on his phone...
He is soon accompanied by Mayuri, who now laments on the loss of her new toy. Rintaro tells her to forget about finding it, but Mayuri's remark about the auctioning price of her new toy made Rintaro change his mind; Mayuri, however, reminds her childhood friend that they would not sell the toy anyway.
All of a sudden, their conversation is interrupted by a blood-curdling scream of a man in the building. Mayuri wonders where the sound came from, but Rintaro decides that it might not be safe and tells Mayuri to leave the building.
Rintaro takes a look himself and discovers that there is a room that has its door ajar. Upon closer inspection, he sees a shocking sight: Kurisu Makise, the young woman who talked to him earlier, is dead, bathing in a pool of her own blood.
A pale-faced Rintaro exits the building, and he could only say a few words to Mayuri about what happened.
"Someone stabbed Kurisu Makise in the eighth floor of Radio Hall."
The sound of ambulance sirens soon interrupt the bustling tempo of people in that stretch of Akihabara road. Although shaken by the incident, he manages to walk away unscathed, only to find himself in another unusual situation when he presses "send" on his cell phone...
Unknown number: 0.571024...
After Rintaro sends a message pertaining to Kurisu Makise's death, he suddenly finds himself alone in Akihabara. He returns to the building where the conference was held — and the place where Kurisu was killed — and finds only Mayuri with his favorite drink. Mayuri appears oblivious to what happened, and this caused Rintaro to be a bit paranoid, but his fears are soon replaced by shock, when the same building he exited a while ago now has what appears to be an artificial satellite crashed on the top of the building.
Rintaro and Mayuri are soon joined by Itaru Hashida, a skillful hacker, and Rintaro "officially" christens his Lab members... in front of a TV monitor which displays the picture of an alpaca with the face of a man. Itaru and Rintaro are initially at odds with each other; Itaru is too busy browsing the Web while Rintaro is busy praising himself.
Soon, Itaru changes the channel to the news using Futuristic Gadget #1 (which is simply a remote control shoved inside a light-and-sound toy gun), where the satellite crash that happened in the Radio Hall is flashed. Mayuri then reminds Rintaro about his supposed reaction on the crash; Itaru even tells Rintaro about how angry the latter was when the conference was canceled.
What's unusual is that Rintaro did attend a conference. However, he concludes that it might be the doing of a certain "Agency".
Rintaro soon finds out that the only TV in their Lab has stopped working, and since Itaru did not want to cooperate, Rintaro is forced to carry the defective TV under the hot sun. He and Mayuri soon arrive and Rintaro demands a rigorous fixing of the TV. The CRT TV shop master Mister Braun agrees to fix it under the payment of a couple thousand yen, which Rintaro is shocked at initially. He soon gives in to Mister Braun's offer and leaves the shop with a disgruntled face. Luckily, Mayuri is there to cheer him up a bit.
Rintaro finally snaps from Mister Braun's "oppression" and asks Itaru to activate Futuristic Gadget #8. Itaru was disgusted with Rintaro's way of talking, but decides to let him do what he wants. The experiment involves bananas, like always, and Mayuri protests to turning bananas she buys into green jelly. However, Rintaro remains stubborn, so Mayuri gives in to the experiment.
As expected, Mayuri's bananas turned into green jelly.
Rintaro soon takes the recluse Itaru outside; although the professional hacker continues on his complaints about being under the sun for too long (in fact, ten minutes), Rintaro heads on. To acquire academic units, they are going to attend a seminar on the Akihabara Techno Forum (ATF) at Dai-Building. Inside, Rintaro discovers by accident that the message that he sent (to Itaru) about Kurisu Makise's death on the 28th is sent five days into the past, on the 23rd.
What shocks Rintaro more is that the subject of the message, Kurisu Makise is standing outside the elevator. He can't believe that Kurisu who is dead is actually alive, in total disbelief.