Reiji is the only heir of the wealthy Suwa family, a line of Japanese traditional dancers living in Kamakura City. The Suwas have operated a dance school in Kanagawa Prefecture for three generations, as well as accumulating a sizeable fortune from their craft. Thus, Reiji had quite a privileged childhood, being able to enter elite institutions as well as gain access to elite programmes. He was raised alongside the children of the Suwa estate's gardener, Shizuma and Asuma Mayuzumi, and the three of them attended the same schools from young. Shizuma is a year above Reiji (until middle school), and Asuma a year below, thus they hung out regularly. However, Reiji ended up being much closer to Shizuma than the younger sibling, in part due to their personalities and in part due to Shizuma taking up the role of Reiji's caretaker/assistant.
The three of them get into stride together during primary school, and specialize in the sport as they get older. Sometime during Reiji's middle school years, an incident occurred that led to Shizuma becoming wheelchair-bound and having to repeat one school year, thus joining Reiji's cohort. We aren't given the exact nature of this incident, only that it was in part due to Reiji's fault. Because of this, Shizuma ended up changing course from being a runner to a relationer (a sort of team coordinator). The three of them end up becoming aces in the sport, and by the time they enter Saisei Gakuen (high school) Reiji ends up being scouted into the school's competing team. The six members of Saisei's best team are expected to perform duties concurrently as members of the school's male idol group, Galaxy Standard, and Reiji's charm quickly resulted in the unit's popularity skyrocketing. In their second year, Shizuma is drafted into the team as relationer. However, Saisei finished in second place for that year, behind Tsubakimichi.
In their third year, Asuma joins the team as well, and Reiji becomes captain as well as the leader of Galaxy Standard. The team is formed proper in April, and they begin training as well as practicing for performances in the same month.