In summer 2020 six months after the Tanegashima Robotics Club saved the world from
Kō Kimijima's Project Atum, Itaru "Daru" Hashida travels to Tanegashima for undisclosed reasons, arriving at the same time as Kaito, who is taking a break from his studies to become an
astronaut. Daru is greeted by Nae, who introduces him to Kaito and the rest of the Robotics Club. Akiho, Subaru, Frau, and Junna have volunteered to help run the local Tanegashima Gun Festival, while Airi continues to live as Kaito's adopted sister. However, at the commencement of the festival, Kimijima reappears using
artificial delusion technology, challenging the Robotics Club to find all of the Geotags he has scattered around the island before he initiates his plan to take over the world. With the rest of the Robotics Club having their hands full managing the festival, Kaito and Daru are recruited to search for the Geotags and thwart Kimijima's plot. However, the Robotics Club begin to notice that this current Kimijima seems less malicious than the one they previously dealt with, as he only seems to use his artificial delusions to commit harmless pranks which seem to only make the festival more popular. Once the festival is halfway done, Daru observes the effects of Kimijima's delusions to figure out that Daru's own delusions were unintentionally influencing Kimijima's actions. Kimijima then becomes hostile and attempts to sabotage the festival, but is thwarted when Daru uses his own powerful delusions to "hack" Kimijima's artificial delusion technology, buying enough time for the Robotics Club to track down and shut down the equipment, seemingly getting rid of Kimijima for good. With Kimijima defeated, Daru and Kaito are free to celebrate the rest of the festival with Nae and the Robotics Club. With Daru's help, Airi, Frau, and Junna are able to overcome their social insecurities, while Subaru finds the courage to make amends with his father over his dream to build robots. Meanwhile, Kaito helps Nae thwart and apprehend an assassin targeting Misaki. He also restarts his relationship with Akiho, after having put it on pause during his studies abroad. With Daru's help, the Robotics Club also rebuilds Gunbuild-2 in time for the final day of the festival, though Kimijima resurfaces in a rebuilt SUMERAGI and attacks. Kai takes control of Gunbuild-2 and supported by artificial delusions provided by Daru, Kai is able to defeat SUMERAGI. Daru then traps Kimijima in a storage device, his true objective this entire time. Daru then returns to Tokyo, where he parts amicably with the Robotics Club. Meanwhile, Misaki is released from the hospital and makes amends with Kaito and Akiho. Upon returning to Tokyo, Daru receives a warning from his friend
Rintaro Okabe, telling him "the worldline trembles." Upon further investigation, Daru realizes that the Kimijima he captured is merely a flawed copy, and the original version of Kimijima is carrying out a series of hacking attacks on supercomputers and infrastructure grids all over the globe, plunging the world into chaos. Daru returns to Tanegashima to consult with the Robotics Club, Sawada, Nae, and Misaki, and they come to conclusion that Kimijima is hijacking the world's supercomputers in an attempt to achieve
technological singularity. Daru uncovers evidence that Kimijima has placed himself inside a satellite. The robotics club fights an army of rogue robots to clear a path to JAXA's space communication center, where Daru proceeds to hack the satellite. He introduces a special program called "ANTARES", which permanently neutralizes Kimijima and prevents him from making any more copies of himself. With the crisis averted, the Robotics Club celebrates, and Daru decides to bring his fellow Lab Members to Tanegashima in the future to meet them. ==Development==