|This article is about a/an ally in Kamen Rider Kabuto.|
- "If I am the world's treasure, this man is the treasure of humanity."
- ―Tendo's thoughts about Jiiya.[src]
Jiiya (じいや) is a butler who serves the Kamishiro family. It seems that the Kamishiro wealth is no more, but Jiiya hides this fact from Tsurugi, finding ways to get money such as getting monetary reward for Sasword's killing of Worms, and after that transaction was cancelled, opening a ramen shop (which Tendo decides to take over as he sees Jiiya as too worthy to be doing this). He tells Kagami about Kamishiro's sister and her death at the hands of the Scorpio Worm. He has a younger twin brother who keeps the Legendary White Knife. He knows that Scorpio Worm is Tsurugi's true form but has chosen not to tell him because Tsurugi, as the last of the famous British Discabil family, must, in one form or another, carry on its name. Jiiya is respected by Tendo who refers to him as "Humanity's Treasure" due to his incredible skill as a chef. He has several students who hold him in high respect, and has published a cook book, which Tendo carries a copy of at all times. During the epilogue, it is revealed that he is the head cook for the Discabil Restaurant, which is owned by Misaki and named in his master's honor. He is 65 years old.
During the first introduction until the end, Jiiya is introduced to be very loyal to Tsurugi no matter how odd is his order. Despite this loyalty, Jiiya also at times scolded Tsurugi if he became naught on losing a challenge, which leads him to get fired at one time until Soji gets them to be together again.
When Arata noticed that Tsurugi was a Worm and informed Jiiya, it was revealed that Jiiya had noticed it for long. He informed Arata that after he knew that Tsurugi's personality able to outwit the Scorpio Worm's will, Jiiya had decided to keep the secret
Jiiya's education towards Tsurugi had a great flaw as he had dotted him too much, leading Tsurugi to lack knowledge about social work, even the economical need. However, Tsurugi learned the truth from Gon and scolded Jiiya for not telling him. Fortunately for Jiiya, Tsurugi decides to help out to get more money (albeit it rarely ending well because Tsurugi never learns the ethic of working in a common society).
He serves Tsurugi and often acts as a parental figure to him. He remains loyal to Tsurugi despite many of his rude actions.
- Exceptional Chef: Jiiya is a talented chef, and one of the few people whose cooking abilities can rival Tendo's. He has written at least one cookbook and has trained several other chefs.