It was after classes, there was a guy with black hair, and black eyes wearing the Cromer school uniform, who looked like he was a side character based solely on the fact that he could blend into the background, and was currently extremely anxious.
He was standing in front of a door... This door where he was about to enter, was the holy land of cute girls, and cool-looking guys, this door leads to a magical place where high-level people gather... He was about to enter the Mercenary Club's clubroom.
Kei Kaido was a guy you could find practically anywhere, he had no distinguishing features, nor did he have a secret ability or a profound family background. He was your ordinary boy who filled up the background. So you might be asking why was he here, in the place where the most distinct characters gathered. Where people who could be the protagonists of a story stay. Why was he an ordinary person here? It was because he was called here.