Conflicted villains: a trademark of Riku Sanjo writing in toku

A key plot in Kyoryuger involves Deboth members doubting the destructive aims of their team and eventually leaving the team: Torin is pretty much the best case, since after seeing the beauty of Earth, he decided to protect it instead of destroying it, and became the worst enemy of the Deboth members, notably his brother Chaos. And, towards the end of the show, Candelira, Luckyuro and even Aigalon also begin to doubt, despite being very loyal generals.

It's interesting to notice that that theme has already been explored a lot in the two other toku show Sanjo was heavily involved in : Kamen Rider W and Kamen Rider Fourze.

In Kamen Rider W, the first main villain, Kirihiko/Nazca Dopant, who even married a member of the Sonozaki, which are the main antagonists, was at first a willing member of the Gaia Memories traffic, but after realizing the ill effects on the city he loves, he rebels, and ends up beibg killed by Saeko Sonozaki, his wife.
Likewise, Wakana Sonozaki/ Claydoll Dopant, wasn't interested in the Gaia Memory business during a long time, having more fun doing her radio show, Healing Princess, and she even became torn about her Dopant nature, notably because of her friendship with Philip/( the intellectual half of W). A key arc is her being torn between Philip and her father, and while she eventually chooses her father's side, becoming willingly involved in the Museum's plans, she did it because she thought it was for the greater good. And at the end, when she learns Philip (who is in fact her lost brother Raito) died to save her, she decided to sacrifice her life to save him, realizing he was the real savior of Earth among the Sonozaki family, by being Kamen Rider W.
The fact that Philip is a member of the Sonozaki family even adds another layer to that theme, as well as the fact that the Sonozaki mother was in fact Shroud, who was secretly fighting the Museum.

While Riku Sanjo wasn't the main writer of Kamen Rider Fourze, he still wrote plenty of episodes, and Fourze had a similar theme with W, the Zodiarts being similar to the Dopants. A lot of Zodiarts are conflicted about their destructive nature, and Gentaro tries as much to be the Zodiarts's friends as he fights to stop them. Even some Horoscopes show a moral side, notably Aquarius (her arc is written by Sanjo) and of course, Pisces who even became an Horoscope to help the Kamen Rider Club. Besides, not unlike Kyoryuger, the heroes have a mentor figure who is, unknown to them, a key member of the enemy clan (Tachibana/ Emoto/ Virgo Zodiarts, one of the first Horoscopes, and the main follower of Gamou, even if he secretly started rebelling, and, like Torin in Kyoryuger, was pretty much the one who created the Riders, Fourze and Meteor)

While those themes have already been explored (Torin has a lot in common with Master Kaku, and Kamen Rider Faiz is pretty much a war between the Orphenochs who want to destroy humanity vs those who want to protect it), Riku Sanjo has a lot of affinity for them.