Kiriya is an easy-going man whose lighthearted attitude hides a sharp intellect and cunning nature. As such, he is a manipulative individual and also a very convincing liar who will use dirty tactics to get what he wants, including deceit and sabotage. His deceitful personality actually developed from the trauma he experienced five years ago when his friend Jungo died from an accident when he freaked out over the possibility of dying from the Bugster infection. He also states to Emu and the others that he just tried to protect all of them from the harsh truth, showing that he actually didn't want his comrades to get hurt.
However, he still cares for his patients as shown when he found out that Nishiwaki's sister was kidnapped by Graphite and also Yoshio. But even then it did not stop from being opportunistic and self-serving. He had the habitual quirk to drape his dull red leather jacket over his shoulders without putting his arms through the sleeves, and to wear round sunglasses whenever he is observing something, but he'll put his jacket on properly and discard his sunglasses whenever he needs to be serious or fight.
Kiriya's fake laugh Kiriya taunts himself.
But despite his tremendous mental strengths, Kiriya suffers from a great deal of pride that he gets from the knowledge he obtains. This in turn causes him to become blind to his own weaknesses and the strengths of the people he believes to have leverage on. When he is serious enough, he won't lie. However, if someone outsmarts him or the situation turns against him to give the impression that he had been lying, he'll resort back to lying. This often leads to him casually claiming that he did in fact lie before instead of trying to defend his innocence, showing that he doesn't really care what other people think of him.
After returning back from the dead, Kiriya's personality doesn't change. His ability of lying is also his greatest advantage, as shown when he feigns his alliegance with Masamune Dan, the latter of whom is unaware of Kiriya's deception after reviving him.
- Unlike the original Kamen Rider stories, Kiriya Kujo is happily responisble for escaping the tragic fate. He remained alive and well.
- Kiriya is also similar to Urataros from Kamen Rider Den-O due to their truth twisting tendencies. Unlike Urataros, whose lies convinces the Primary Rider, Kiriya is subjected to being called out even by Emu.