He was the king of the demon world that had been laid off because of complaints. She was the hero that had lost her position because she failed in her crusade. Fate bound these two together, and they began a journey filled with mysteries and to pay off their debts.

Haruyuki Arita is an overweight, bullied middle schooler who finds solace in playing online games. But his life takes a drastic turn one day, when he finds that all his high scores have been topped by Kuroyukihime, the popular vice president of the student council. She then invites him to the student lounge and introduces him to "Brain Burst," a program which allows the users to accelerate their brain waves to the point where time seems to stop. Brain Burst also functions as an augmented reality fighting game, and in order to get more points to accelerate, users must win duels against other players. However, if a user loses all their points, they will also lose access to Brain Burst forever. Kuroyukihime explains that she chose to show Haruyuki the program because she needs his help. She wants to meet the creator of Brain Burst and uncover the reason of why it was created, but that's easier said than done; to do so, she must defeat the "Six Kings of Pure Color," powerful faction leaders within the game, and reach level 10, the highest level attainable. After the girl helps Haruyuki overcome the bullies that torment him, he vows to help her realize her goal, and so begins the duo's fight to reach the top. [Written by MAL Rewrite]

In junior high, Ryou Mizushima and his friends join the badminton club on a whim. As he grows fond of the sport, Ryou works tirelessly to improve his badminton skills until he qualifies in the prefectural tournament. Lacking a coach who can bring out his full potential, he does not consider entering a high school with a strong badminton team. Instead, he plans on attending a local high school where he can play badminton for fun. However, Ryou's perspective changes when Yokohama Minato High School's badminton coach scouts him. Not only does the institution have one of the strongest badminton teams in the region, but it also has Kento Yusa, a player Ryou admires. Though hesitant at first, Ryou decides to enroll with the support of his sister. Possessing a firm ambition, he begins to gain experience with the proper guidance of a coach—all in hopes of surpassing Yusa one day.

The Yuzuki family, which consists of four brothers, lost their parents two years ago. Hayato, the eldest son, is a hard worker and the pillar of the family. Mikoto, the second son, is calm and collected, but he has a soft spot for his younger brother Minato, whom he adores and thinks is cute. Minato, the third son, is energetic and adores his brothers, but he is clumsy and awkward. Gakuto, the fourth son, is a studious and mature first-grader who is often referred to as a "wise man." The manga depicts the four brothers' daily lives as they navigate their family, school, and community.