According to the official website of the anime “A Certain Scientific Railgun T” , the second part of the 3rd season of the anime will feature the arc called Dream Ranker.
In addition, the following promotional image was also released:
Synopsis : Academy City is a highly technologically advanced place, said to be 20 to 30 years ahead of the rest of the world. Eighty percent of its 2.3 million residents are students. But the focus of studies here is on esper powers. Misaka Mikoto, one of the city's most respected, shares a room with Kuroko Shirai, another high-level esper who is a member of Judgment, a student-run law enforcement agency. Both attend Tokiwadai, a private school reserved for high-ranking and wealthy students. Kuroko's partner at Judgment, Kazari Uiharu, is a low-level esper who attends Sakugawa High School. Her best friend and classmate is Ruiko Saten, a level zero (no esper powers). Together, the four encounter various adventures in the exciting science city. (Via: Crunchyroll )
The third season of “ A Certain Scientific Railgun T” will have a total of 25 episodes, however, it is on hiatus due to COVID-19.
Source: ANN
