SI-VIS is a co-ed music group, led by Yosuke, shaking up the global music scene with their unmatched vocals and performances. However, they are actually heroes in disguise, battling against mysterious forces threatening the world. They convert audience energy at live performances into combat power. Luckily, the battles appear to be ordinary concerts to the public, keeping their identity a secret.

The anime series is set in the future when humanity migrated to the Moon due to Earth's climate change. It will incorporate original elements unique to the anime, such as human drama about survival, and will feature a diverse field that blurs countries and eras such as Shibuya, the Edo-period era, and London.

Once a prize-winning violin prodigy, Hajime gave up on music after his father, professional violinist Ryuuji Aono, was involved in a scandal that led the media to harass his family. Now living alone with his mother and entering his final year of middle school, Hajime struggles to find a new career path. However, the sound of his classmate Ritsuko Akine playing the violin inspires Hajime to dream of a musical career once more. With the help of Ritsuko, Hajime prepares to take the entrance exam for the prestigious Umimaku High School. But if he wishes to join Umimaku's orchestra, Hajime must overcome his past trauma and open himself up to new musical horizons.

The protagonists of the series are the three Kisugi sisters—Hitomi, Rui and Ai—who run a café called Cat's Eye. The sisters lead a double life as a trio of highly skilled art thieves, leaving cards with the name "Cat's Eye" at the scene of their crimes. They steal works of art that belonged to their long-missing father, Heinz who was a famous art collector during the Nazi regime, in the hopes of him contacting them. Toshio, the police officer investigating this case is the fiancé of Hitomi. He also swears to capture and bring down the Cat's Eye Gang.