The Holy Rangers are constantly battling the evil organization Gladios, a conflict deeply woven into their daily lives. The team consists of four siblings: the commander and eldest brother Holy Red, Seizaki Ryuya; second brother Holy Black, Shiro; eldest sister Holy Blue, Runa; and youngest sister Hikari, who serves as the communications officer. One morning, during the rare occasion when all siblings are gathered together, Hikari expresses her desire to become a full member of the Holy Rangers. Immediately afterward, an urgent report arrives—Gladios forces have split into three groups and begun destructive attacks. The team must now rise to face this new threat.