As we know, A lot of TV anime announcements happened during the Dengeki Bunko Winter Festival Event. A Light Novel Series “Reign of the Seven Spellblades” which is “Nanatsu No Maken ga Shiahi Suru” in Japan by Bokuto Uno is going to be adapted into a TV anime series. Well, this story is based on Alderamin On The Sky which is quite a popular book.

Furthermore, The first volume of this Light Novel Series is published in September 2018. In September 2021, the Light Novel gets the 8th volume of its series. Additionally, After Light Novel, it got adapted into a Manga Series by Sakae Esuno in Shonen Ace magazine.
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The English translation of Reign of the Seven Spellbladesis done by Yen Press Publishers. Here is a synopsis of the story by Yen Press Publishers:
Springtime at Kimberly Magic Academy, when new students begin their first year. One boy, clad in black robes with a white cane and sword strapped to his hip, approaches the prestigious school. This young man—Oliver—must form a bond with a katana-wielding girl named Nanao if he’s to survive the dangers he’s to face at this school that is anything but what it seems!
Yen Press
Source: Mantan Web via Anime News Network