Kamen Rider writers : late Showa era

1)  The "Kamen Rider" reboot era.

After Kamen Rider Stronger, the Kamen Rider franchise seemed over on TV. However, four years after the end, Ishinomori decided to revive the Kamen Rider franchise, and the new series, airing in 1979 was pretty much a reboot of Kamen Rider, even calling itself "Kamen Rider" like the original; fans often call that series "Skyrider" after its main character, who's able to fly once transformed to avoid the confusion with the original show. Even the villain group was pretty much a reboot of the  original villain group of Kamen Rider :  "Neo-Shocker". Skyrider had also several veterans Riders making appearances through the show, in special episodes. The following year, a new Kamen Rider series, Kamen Rider Super 1 aired, keeing the continuity with Skyrider by keeping a mentor like figure, Genjiro Tani (who was pretty much the replacement ofr Tachibana). However, the rebooted Kamen Rider franchise only lasted two years on TV, and Kamen Rider went again on hiatus after Super 1.

Masaru Igami came back as main writer for Skyrider, but in Super 1, he only remained as secondary writer, letting one of his secondary writers, Takashi Ezure become the main writer

Kamen Rider (Skyrider) (54 episodes)
Masaru Igami (head writer) : 1-5, 7-9, 12-14, 16-21, 23 (18 episodes)
Kimio Hirayama : 6, 10, 15 (3 episodes)
Takashi Ezure : 11, 25, 30-32, 36-37, 43, 45, 47, 52-54 (13 episodes)
Katsuhiko Taguchi : 26-28 (3 episodes)
Katsuhiko Takada : 22, 29, 34-35, 38-41, 44, 48-49 (11 episodes)
Kyoko Sagiyama : 24, 33, 42, 46, 51 (5 episodes)
Seirou Suzuki : 50 (1 episode)

Kamen Rider Super 1 (48 episodes)
Takashi Ezure (main writer) : 1-3, 6, 9, 12-13, 16-17, 21-25, 29, 34, 38, 41, 46-48 (21 episodes)
Katsuhiko Takada : 4-5, 8, 10, 14, 18, 27 (7 episodes)
Kyoko Sagiyama : 7, 19, 31, 44 (4 episodes)
熊谷節 : 11, 15, (2 episodes)
Masaru Igami : 20, 26, 28, 30, 32, 35, 37, 39, 42, 45 (10 episodes)
Sukehiro Tomita : 33, 43 (2 episodes)
吉田耕助 : 36-40 (2 episodes)

A little analysis : Masaru Igami came back as head writer in Kamen Rider Skyrider, but, interestingly, it seems he pretty much left in the middle of the series, as if the series had a change in head writer in the middle of the show; interestingly, it's at the same time that one of the secondary writer, Hirayama (who is also an episode director), stopped being involved as well. At that time, the one who pretty much took over as head writer seemed to be Takashi Ezure, who wrote the most episode afterwards, and with him, two important secondary writers came: Katsuhiko Takada, who wrote a similar amont of episodes as Ezure did, and Kyoko Sagiyama.
Ezure would become afterwards the main writer of Super 1, and would keep Takada and Sagiyama as important secondary writers. However, interestingly, Igami came back in the second half of Super 1 to become again a major secondary writer, pretty much taking over Takada who stopped being involved in the writing after episode 27. Igami wrote the most episodes after Ezure.


2) The Kamen Rider Black era

After a 6 year Hiatus, the Kamen Rider franchise came back again on TV. Once again the franchise was rebooted, but this time, the series would have no link to its predecessors, and while its concept was similar to its predecessors (the hero being modified for an evil organization, Gorgom), the story had completely new characters, and the heart of the story being the confrontation between the hero Minami Kotaro, who escaped the evil organization and became Kamen Rider Black, and his  brainwashed brother figure who couldn't escape and was successfully brainwashed, Nobuhiko Akizuki, who became his worst enemy as Shadow Moon. Kamen Rider Black ended in a bittersweet ending, with Gorgom being destroyed, but Kotaro was forced to defeat Shadow Moon and he ended up alone.
Kamen Rider Black was so successful it was followed by a direct sequel, Kamen Rider Black RX, who followed the adventures of Minami Kotarou after the first show, and his fight against the Crisis Empire. Black RX was more light hearted, and very often felt like a fantasy show similar to some Metal Hero shows, especially given the Crisis Empire felt like a classic Metal Hero villain group (it's telling that the actress playing Maribaron, a major antagonist, plays regularly villainesses in the Metal Hero franchise). Despite the short return of Shadow Moon, the introduction of several forms for the main hero (a concept which would be used a lot later), and, in the last arc, the return of the veterans Riders, Black RX wasn't popular enough to allow the franchise to go on, and Kamen Rider would start its longest hiatus on TV, with no new series for more than 10 years, until Kamen Rider Kuuga.

Kamen Rider Black was the first Kamen Rider series where Masaru Igami wasn't involved, confirming once again how the show was supposed to be in a new era. Interestingly, the Black era was the first era where most of the writers were (or would be) involved in the twoother major Toei toku franchises : Super Sentai and Metal Hero.

Kamen Rider Black didn't have a head writer from beginning to end : Shouzo Uehara started writing the show, but left after writing a few episodes, and it seems that the ones sharing the job as head writer were Sugimura and Miyashita.
It's interesting to notice that the writers who were the most involved in Kamen Rider Black were pretty much the three most important Metal Hero head writers, Uehara, Sugimura and Miyashita.
Those three were also heavily involved in the Super Sentai franchise, Uehara and Sugumra being major head writers at two different eras, and Miyashita becoming had writer of Hurricanger.
Interestingly, two secondary writers from the previous era came back: Katsuhiko Taguchi and Kyoko Sagiyama. Sagiyama was also involved as secondary writer in the sentai franchise and would be then become an important Metal Hero secondary writer. A major tokusatsu writer also made his debut in Black : Naruhisa Arakawa.

In Kamen Rider RX however, the head writer would be a veteran Kamen Rider writer, who was very involved in the first reboot era : Takashi Ezure. Miyashita and Sagiyama stayed as secondary writers, and another writer, Kenichi Araki was involved as well. Unlike in Kamen Rider Black, RX had its head writer staying from beginning to the end, handling more than half of the episodes (the first one to do so).
The Kamen Rider Black era were the first toku shows where Miyashita would have a major involvement : he is with Sagiyama, the only one who wrote a significant number in both Black and RX, and he would become later a major Metal Hero head writer.

Kamen Rider Black (51 episodes)

Shouzo Uehara (first major writer) : 1-4, 12 (5 episodes)
Junichi Miyashita (second major writer) : 5, 9, 15, 22, 29, 31, 33, 37, 41, 45, 48, 49 (12 episodes)
Makoto Naitou : 6, 10 (2 episodes)
Takashi Yamada : 7, 11, 18-19, 39, 42 (6 episodes)
Kyoko Sagiyama : 8, 16-17, 23, 27, 30, 40, 44 (8 episodes)
Noboru Sugimura (third major writer) : 13, 20-21 (with Kenichi Araki), 26, 34-36, 38, 46-47, 50-51 (12 episodes)
Katsuhiko Taguchi : 14, 25 (2 episodes)
Kenichi Araki : 20-21 (with Sugimura), 43 (3 episodes)
山口竜 : 24, 32 (2 episodes)
Naruhisa Arakawa : 28 (1 episode)

Kamen Rider Black RX (47 episodes)

Takashi Ezure (main writer) : 1-7, 14-18, 20, 25-26, 29-30, 37-38, 41, 44-47 (24 episodes)
Kenichi Araki : 8, 19 (2 episodes)
Kyoko Sagiyama : 9, 13, 23, 28, 31-32, 42 (7 episodes)
Junichi Miyashita : 10-12, 21-22, 24, 27, 33-36, 40, 43 (with 村山隆策) (13 episodes)
Takashi Yamada : 39 (1 episode)
村山隆策 : 43 (with Miyashita) (1 episode)