Her Majesty's Swarm: Volume 3

Grevillea, Queen of the Arachnea, has rapidly decimated the Kingdom of Maluk and now the Dukedom of Schtraut. After receiving troubling reports that the shores of her newly obtained territory are being raided, she investigates the matter. She discovers that these raiders are pirates under the command of a female captain named Isabelle. The pirates belong to a colony on the island of Atlantica, and they are a formidable faction not to be trifled with. Grevillea conspires with Isabelle and improves her navy. Strengthened by this partnership, she aims to plunge the Popedom of Frantz into the depths of despair...

[From J-Novel Club]