Niwakawa has been a fan of Regao for ten years. One ordinary day, when he was about to go out to eat rice noodle rolls, he was sent to the Regao world by a truck that was supposed to take the boy next to him to another world due to a novice driving error. From then on, he embarked on a journey of glory with a pair of fists. First, he followed Serizawa to dominate Suzuran in the first year. In the second year, he fought a legendary battle with Bouya Harumichi and Hayashida Megumi. In the third year, he became the first man to dominate Suzuran. After graduation, he joined the Kowloon Buddhist Association. With his powerful strength, he became the wakagashi of the Buddhist Association. After helping the Kowloon Association to unify the sword area, he became the strongest combat force of the Kowloon Association. Under his leadership, the Kowloon Association successfully defeated powerful enemies one after another and became a truly terrifying Dark Empire.

A former key server for a university volleyball team accidentally travels to the world of Haikyuu Shonen and restarts his life. This time, he is no longer willing to be that unknown key server. He becomes the team's ace, the absolute main force in the hearts of his teammates, and leads his teammates from Karasuno to dominate the country!!!