The anime will depict the lively everyday lives of the demon brothers through special episodes separate from the game’s main story (Lessons).

In the eyes of the public, Fudou Aikawa and Desumi Magahara are sworn enemies who have nothing in common. Fudou, also known as "Red Gelato," is the leader of the hero squadron "Gelato 5," whose mission is to bring about world peace. On the other hand, Desumi is the minion leader of "Gecko," a villainous organization seeking world domination. However, despite these differences, their relationship is not quite what it seems. When they are not making a show of being at each other's throats, Desumi and Fudou continue to pursue a forbidden love. Going on dates, baking sweets for one another, and meeting up as often as they can despite their hectic schedules, the two inexperienced lovebirds pave the way for their own unique relationship. Though their public lives are worlds apart, Fudou and Desumi will stop at nothing to make their seemingly impossible romance work.

In 2019, a rift to another dimension suddenly opens in the skies above, revealing a "turnabout" alternate world called "Shinkoku Nippon." This parallel version of Japan maintained its militarism and remains stuck in the Showa era. Shinkoku Nippon invades our Japan with its "Genmu" gas weapons and giant humanoid "Garan" weapons. The invaders immediately take over our government and all but conquer Japan. As a result, our Japan never ushers in the Reiwa era. A decade later, our Japan has been revamped as Genkoku Nippon, a puppet state of Shinkoku Nippon. Under harsh censorship, the once thriving manga, anime, idol, and similar sub-cultures have completely died off...or so it seemed.

Shoutarou Hidari, a hard-boiled private investigator from the Narumi Detective Agency, lives for the sake of protecting the peace in the city of Fuuto alongside his inquisitive partner, Philip. One fine night, Shoutarou encounters a mysterious woman named Tokime, who is soon linked to several cases of homicide and theft. Shoutarou's investigation leads him to people using "Gaia Memories"—memory units similar to thumb drives holding vast amounts of data—to turn into formidable beasts called "Dopants." While the majority of Gaia users were put down by the detective team in the past, a number of them still remain, posing a great threat to public safety. Once more, Shoutarou and Philip, Gaia users on the side of justice, must fight as Kamen Rider W—the renowned hero safeguarding Fuuto—to eradicate the nest of villainous Dopants, all while uncovering Tokime's true identity and confronting the long-forgotten past.