Before Zero Day took place, Kiriya discovered through files he took from the Ministry of Health that his friend Jungo Aihara had been afflicted with a mysterious sickness - the Game illness, which was a potentially fatal virus. Informed by Kiriya of his findings, Jungo was unable to accept the reality that he was going to die and freaked out and ran away, leading to his death in a traffic accident. Kiriya was devastated by the passing of his friend, and grieved over Jungo at the morgue. He blamed himself for revealing the truth, and lamented that his friend would not have died had he kept it to himself. Consequently, the incident caused Kiriya to believe that telling the truth might not always be the best thing to do.

Two years later, Kiriya Kujo found out about Zero Day and the Bugster three years before the series. Confronting Kuroto Dan about this information, he blackmailed Dan into giving him a Gamer Driver and the Bakusou Bike Gashat in exchange for his silence.

A further three years later, Kiriya watched from the sidelines following the Count Salty's rampage, voicing to himself that things are getting interesting and that everyone is raring to start the race.

From afar, Kiriya later witnessed Ex-Aid and Brave's battle against the Aranbura Bugster which was interrupted by Kamen Rider Genm, observing that everyone is getting "super pumped up".

Seeing Snipe's debut, he noted that it was about time to start the race.

Revealing himself to Emu under the pretense of saving an infected coworker Kiyra faces trouble at every turn, his level 2 form being a bike that needs a rider to function at 100% and his own run ins with Genm ending badly. While he and Emu are able to save his coworkers kidnapped girlfriend from Motors he never gets a break and it isnt until Kuroto convinces Graphite to part with Giri Giri Chambara and Jet Combat to “even the playing field” that he gets a humanoid form but the celebrations are short lived as once the Power Players and notably Extreme enter the fight he, Kuroto, and Radiologist and fellow rider Kiro are killed.

Facing the judge of the Afterlife Kiyra is given a second chance with a Ghost Driver and a quest to find 15 Eyecons in 99 days or his life would be over forever he strangely sticks close to Kuroto not believing the story he gave to Tenkuji Takeru in the slightest on why he would help the riders as Paladin and hunt them as Genm.

Sticking close to Kuroto Kiyra eventually earns enough trust to be granted the Bakasou Tour and Rider Rumble gashats which circumvent the 99 days timer and give him a new lease on life as a Bugster, he continues to hang close to Kuroto in the background acting as backup and ally but not really interfering as he continues to silently gather data, watch and observe.