On a rainy afternoon, a male high school student awakens freezing on the streets with no memory of how he got there. His classmate and crush, Karen Inukai, finds him and takes him back to her home where, to his surprise, she starts to undress. She seems intent on bathing with him, though he has no idea why. When she holds him once more, he catches a glimpse of himself in the mirror—discovering that he has turned into a dog! Inukai adopts the puppy and names him Pochita. Now, he must adjust to life as a dog and figure out how to get out of this strange predicament. But while he mulls over an escape plan, Pochita sees a whole new side to Inukai that he never saw at school.

After fighting to free the game of soccer in Japan from the Fifth Sector, the country's soccer squads can once again look forward to stepping onto the field. However, a new challenge will emerge for Japanese players in the form of the Football Frontier International Vision 2, a new tournament that will bring together the best teams each country can assemble. Tenma Matsukaze and his Raimon teammates, Takuto Shindou and Kyousuke Tsurugi, are once again part of the action as they have been selected to play for the Japanese representative, Inazuma Japan. Much to their surprise, the coach selects eight other players that have no previous experience playing soccer! Team Inazuma Japan will have a huge mountain to climb, building chemistry and skills as they go along. What they don’t know is that the tournament will set the stage for something much bigger, something out of this world in Inazuma Eleven Go: Galaxy!

Takumi Fujiwara finally joins Ryousuke and Keisuke Takahashi to create Project D. Their goal is twofold: Ryousuke wants to develop his High-Speed Street Racing Theory, while Keisuke and Takumi aim at improving their driving skills by facing powerful opponents on dangerous roads. The idea of Project D is to challenge street racing teams from other prefectures to improve both their uphill and downhill records. In order to attract the attention of the best racing teams, Ryousuke creates a dedicated website to announce the future battles of Project D and post the team's results. The fourth season of Initial D details the hardships and successes of the members of Project D as they try to become the best street racing team outside of Gunma Prefecture.

After earning a series of difficult victories in the prefectures of Tochigi, Saitama, and Ibaraki, the drivers of Project D—an amateur street driving group led by ex-street driver and expert tactician Ryousuke Takahashi—Takumi Fujiwara and Keisuke Takahashi now have to take Project D to the next level: the Kanagawa prefecture, commonly known as the holy land of street racing. Their opponents, members of the three best street racing teams of Kanagawa, design an elaborate strategy called the Four Lines of Defense to put a definitive end to the ambitions of Project D. Meanwhile, Takumi feels he needs to refine his driving skills to overcome the last victory against Toshiya Joushima that he only just managed to snatch. The moment of truth has now come for Project D, which carries with it the hopes of the Gunma Prefecture; will they manage to thwart the surprising tactics of the skilled street racers of Kanagawa?