|This article is about a/an character in Kamen Rider Ex-Aid.|
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.
Behind the scenes
Yoko Horiuchi is portrayed by Mami Kamura (加村 真美 Kamura Mami).