After losing both parents in a fatal plane crash, teenager Ryuuichi Kashima must adjust to his new life as the guardian of his younger brother Kotarou. Although Ryuuichi is able to maintain a friendly and kindhearted demeanor, Kotarou is a reserved toddler still too young to understand the reality of the situation. At their parents' funeral, they are approached by Youko Morinomiya, the stern chairman of an elite academy, who decides to take them under her care. However, there is one condition Ryuuichi must fulfill in exchange for a roof over their heads and enrolment in the school—he must become the school's babysitter. In an effort to support the female teachers at the academy, a babysitter's club was established to look after their infant children; unfortunately, the club is severely short-staffed, so now not only is Ryuuichi responsible for his little brother, but also a handful of toddlers who possess dynamic personalities.

In Tokyo Fire Department's Fire Academy, a talented new rookie is excelling in the strict and grueling rescue training. With high proficiency in both physical and mental categories, Daigo Toake is envied by one of his peers, Shun Onoda. Despite feeling a growing sense of rivalry, Shun recognizes that a part of his jealousy stems from his admiration for Daigo, and that they will eventually work together for the same noble goal of rescuing people. At the same time, Yuki Nakamura is the only woman among the current batch of recruits. She believes that she will not be outclassed in this male-dominated profession. As the fates of the three newbies intertwine, they may soon realize that the intensity of a real disaster is nowhere near what they have experienced in training. Even so, the heroes in orange will always shine brighter than any fire, saving those in need.