|This article is about a/an character in Kamen Rider Ex-Aid.|
Nishiwaki was infected by Graphite, who subsequently kidnapped his sister to aggravate Nishiwaki's stress. The coroner was found quickly by his co-worker Kiriya Kujo. His infection flared into a spiked wheel Bugster Union that was destroyed by Lazer Bike Gamer Level 1, releasing the Motors Bugster. Motors was soon destroyed and Yoshitaka cured by Ex-Aid and Lazer Action and Bike Gamers Level 2.
- "Has something happened to Kiriya? I mean, I haven't been able to contact him for a while, so I'm worried."
"So are we, that is why I came here to find clues."
- ―Yoshitaka and Hiiro[src]
The Bugster Union (バグスターユニオン Bagusutā Yunion) is the monster form of a Bugster-infected patient when the virus first flares up. When a Bugster-infected patient experiences enough stress, the Bugster Viruses inside multiply rapidly and overtake the patient's body, forming a giant orange virus form around it; the Union's shape seems largely irrelevant to the Bugster's appearance. Bugster Unions can only be defeated by a Kamen Rider in Level 1; the reason why is unexplained, though it may be because other Levels are too strong and may injure the patient inside the Union.