The Legendary Witch Is Reborn as an Oppressed Princess: Volume 3

Two years have passed since Claudia said goodbye to her wayward student Sewell. Now ten years old, she brings Noah with her to enroll in Raushneur Academy of Magic: an institution she—as the great witch Adelheid—had built on the bottom of the sea five hundred years ago! She and Noah travel there to investigate a mysterious song that lures ships to their doom. They meet Fiolina, an eighth-year student with a beautiful voice and a royal secret, as well as Fiolina’s younger sister Lauretta, who has trouble controlling her tremendous magical power. Claudia believes that the key to solving the curse’s mystery lies with these two sisters. To further complicate matters, Noah’s cousin Sieghart, the Crown Prince of Lemilsia, is also a student at the academy! Join Claudia and Noah as they journey to the bottom of the sea to continue their quest to eliminate curses the world over!

[From J-Novel Club]