Starting from Kaiwu, the reason is that most of the current Kamen Riders have returned after Kaiwu.
Moreover, Kaiwu is not a unit drama. It is easy to watch Knights such as Build. Each story of Kamen Rider is independent, with different protagonists, different systems, and its own story. There is no problem of not understanding the order, just choose and read as you like.
Extended information
Series history
The "Kamen Rider Series" is a tokusatsu TV series that started in 1971 and was originally created by Shotaro Ishimori and produced by Toei. . After the first "Kamen Rider" series was aired on April 3, 1971, it was loved by audiences of all ages and led to more subsequent Kamen Rider works.
The protagonist "Kamen Rider" was originally designed by manga artist Shotaro Ishimori, and was planned and named by Hiroshi Hirayama and Seiji Abe of Toei. Therefore, the Showa Kamen Rider series will be marked with the original "Ishimori Shotaro" to commemorate him.
After Shotaro Ishimori passed away on January 28, 1998, the Heisei Kamen Rider series and the Reiwa Kamen Rider series created by Toei Co., Ltd. will also indicate the origin of the original "Ishimori Shotaro". Remember him.
Kamen Riders are currently divided into three categories: Showa Knights, Heisei Knights and Reiwa Knights. From the first work "Kamen Rider" to "Kamen Rider J", they are all stories about the confrontation between cybernetics who undergo transformation surgery and evil organizations. They are classified as Showa Riders.
The Kamen Riders who appeared from "Kamen Rider Kuuga" to "Kamen Rider Zi-O" are classified as Heisei Riders. The Kamen Riders who appeared in "Kamen Rider Zero-One" are classified as Reiwa Riders.
Baidu Encyclopedia-Kamen Rider