Following the events of Kamen Rider Genms -The Presidents-, Gai Amatsu has managed to set up a proper office for his new company, Thouser-Intellion. He revives Kuroto Dan by giving him a Humagear body to possess. Chaos ensues.

Kamen Rider Genms -Smart Brain and the 1000% Crisis- (Kamen Raidâ Genmuzu - Sumâtoburein to Sen-Pâsento no Kuraishisu -) is a TTFC-exclusive crossover special between Kamen Rider Ex-Aid and Kamen Rider Zero-One, while also featuring elements of Kamen Rider 555. Serving as a sequel to Kamen Rider Genms -The Presidents-, Gai's journey to learn more about Genm Corp. has its consequences when he faces a revived Kuroto Dan once again.—Kamen Rider Wiki

In this sequel to "Kamen Rider Genms -The Presidents-", after overcoming the gamer disease, Gai Amatsu used the President Progrise Key to train a Humagear to learn how to become the president of Genm Corporation. As expected, the Humagear gets infected by Kuroto Dan's Bugster Virus and thus, Kuroto Dan gets revived. Gai tries to tell Kuroto of the purpose of his resurrection, but he ignores all reason. Gai acquires a new Driver to achieve his goal. This new Driver transforms Gai into Kamen Rider Thousand Ark, but he is not the only one with new toys as Kuroto also transforms into his new form, Kamen Rider Genm Musou Gamer.—TheTVDB