Due to a weak heart, Suzune Miyama has remained bedridden for most of her childhood. However, despite her illness, she has always dreamed of becoming an idol. Eventually, her opportunity comes in the form of the seventh Selection Project—a brutal series of competitions best known as the starting point of the legendary idol Akari Amasawa. Anxious but excited, Suzune enters the preliminary round of Selection Project. Though her singing dazzles the judges and her fellow competitors, Suzune is unfortunately overcome by her nerves and freezes up in the middle of her performance. She recovers quickly, but the stumble is great enough that she loses the winning spot and is disqualified. Or so it seems—until Seira Kurusu, the girl Suzune lost to, announces that she plans to drop out of Selection Project, believing Suzune is a more talented singer and therefore deserves the right to compete. Suzune is caught off guard by the decision, but promises Seira that they will meet again as top idols. She prepares herself for the challenging obstacles that lie ahead.

After losing his mother at a very young age, elementary school student Capeta Taira is forced to become more independent to avoid his father worrying for him. Working in a paving company, his father is often busy and has to work overtime to make ends meet. However, no matter how tough he acts in front of his father, Capeta is ultimately just a lonely kid with a rough life. In addition to his typical house duties, he has to deal with the bully Nobu Andou which makes him feel worse, despite support from his classmate, Monami Suzuki. One day, Capeta's father sees young go-kart drivers racing at high speeds and gets inspired by the scene. He then decides to collect scrapped parts available on the track and begins working on a gift for his son. Meanwhile, Capeta and Monami sneak into his workplace, suspecting that his father is up to something. Much to their surprise, they see a go-kart built from discarded parts—with Capeta's name attached to it! Although it lacks an engine and looks worn out, the kart is mostly complete and functional. Despite the heavy rain, Capeta cannot resist the urge to try out this new machinery. As he drives the kart downhill on a wet road, an incident that is almost a dangerous accident instead becomes a thrilling obsession. No longer bored with life, the engine of Capeta's heart is ignited with a new passion as he journeys into the world of racing.

A lot has happened for Nagi Umino and Erika Amano: they were swapped at birth, learned of their engagement, and have started living under the same roof. The two now share their home with Nagi's sister, Sachi, and his crush, Hiro Segawa. Despite this unusual domestic situation and frequent quarreling, the group is beginning to settle into a life together. However, the return of Nagi's childhood friend Ai Mochizuki to Japan complicates things. Ai suddenly declares her intention to marry Nagi, and although he turns her down, she is committed to having him all to herself. Now with four girls around, each with their own thoughts about him, Nagi must figure out his own feelings and the best way forward.

Humanity and demonkind have been on bad terms for millennia, resulting in the continent of Leunders being split in two. Although the situation has stabilized between the races, the fragile peace breaks when the new demon king launches a fierce all-out attack. With all of the non-demon nations falling to the violence in under a year, humanity's hope rests in a special squad, led by swordsman Kyle Leonard, that must assassinate the demon king in order to bring an end to the war. During the dangerous mission, Kyle ends up in a clash with the demon king that brings him to the brink of death. As Kyle realizes he has lost everything he wanted to protect, a mysterious gem transports him back in time before the conflict even started! Now with knowledge of future events and a strong desire to save his loved ones, Kyle sets out to become even stronger to prevent the extinction of humanity.