|This article is about a/an character in Kamen Rider Kabuto.|
A mysterious person who quotes animal stories and occasionally the Bible, he is also the police Commissioner. He is a highly trained fencer and plays the cello. Arata seems to despise him because of Ryo's disappearance, as well as the lack of concern or activity done in order to find Ryo. Arata is also unaware that his father is even part of the organization, ZECT, let alone the leader. It seems that he has a very secret agenda and would even sacrifice his sons to achieve his goals. Tendou later confronted Riku; the confrontation ended with Riku telling him that Tendou's sister (actually refers to Hiyori, not Juka) was not in good hands, which naturally made Tendou lose his composure, and Riku walked off, joking about Tendou's "walking down the path to heaven to rule over all".
During the end of episode 36, he displays that he indeed knows about the Hopper Riders, saying they have opened the Gates of Hell. He also says the Rider's grand plan will be completed by our sons, showing that he did indeed know Tendou's father. He tells Kagami of the secrets behind the Masked Rider System in episode 41, displaying his knowledge of the Natives and how they created the system. He also tells Tendou that his father was the one who installed the Red Shoes system (which allows a person to force either of those Riders to act against their will) in the Kabuto and Gatack Zecters, and in turn, Tendou decides to trust him because he too desires to walk the path his father took.
He is overthrown from his leadership position at ZECT by Mishima after he learns of the Red-Shoes system implemented in the Kabuto and Gatack Zecters. Mishima and Negishi realize that Riku is not on their side. He is still alive in the epilogue watching his son grow up. It is likely he is now simply the chief of police. 52 years old.
Riku is shown to be a calm individual without any true emotions to be shown throughout the series progress until Mishima took over the ZECT Foundation. Behind his calm manner and cunning, he is in fact a very loving individual, showing that he cares of Souji Tendou and his sons. His calculative mind even surpass Souji, showing that he knew Souji in disguise by telling him about how well is his sister during their first encounter.
- Charisma: Riku's calm, polite, and great decision to face problem lead many people respect and depend on him, even the Natives who are accepting humanity. This charisma even feared by Mishima and some Worms who recognize him.
- Master Cullinary Judge: Riku once shown to be able to judge the foods which are provided to him so he could serve his guests on big party the best cooking from the chef he deemed fit. This also lead Riku somehow own an illegal dark cooking duel ring and becoming the judge of it.
- Even though he is portrayed as somewhat of a villain who wants to bring down Kabuto and the other Riders not affiliated with ZECT, he reveals to Kagami that he has always been on the side of humanity. It is possible that he always knew that Mishima and Negishi were not to be trusted, but too powerful to confront, so he continued an agenda that fit to their favor, hoping Kagami and Tendou would find a way to kill the Worms and stop the Natives.