Witches are the most feared beings in the world, capable of summoning floods, conjuring fire, and destroying entire countries. This terror is why everyone wants Siasha, known as the Silent Witch, dead. After yet another violent battle for her life, she encounters Zig Crane, a skilled mercenary known as the Double-Bladed Mercenary, who had been hired to kill her. Following a fierce confrontation where Zig emerges victorious but finds his employer dead, he hears Siasha's plea that she only fights to survive. Instead of finishing the job, Zig agrees to a new contract: Siasha will hire him as her bodyguard.

The pair decides their best hope for peace lies far from their war-torn homeland of Vasterre. They set out for a mysterious and largely unknown continent called Outre-Terre, a land recently made accessible by new seafaring technology. Their voyage, however, ends in disaster when their expedition ship is wrecked, leaving Zig and Siasha as the apparent sole survivors on a shore teeming with ravenous monsters.

The new continent is a harsh and untamed wilderness, dominated by vicious creatures known as Malebets, which must be constantly culled. In this land, the endless war between humans is absent, as all civilized efforts are focused on survival against monstrous threats. Consequently, there is no work for a traditional mercenary. Instead, society is organized around a guild of adventurers who hunt monsters. To navigate this new life, Siasha registers as an adventurer, while Zig remains her unofficial guardian and protector.

This strange land also holds unexpected revelations about magic. While Siasha is an anomaly in her homeland, where magic is the sole domain of reviled witches, on this new continent, the ability to use at least a little magic is common to everyone. This fundamental difference forces both characters to adapt. Siasha, who is over two hundred years old and longs for intellectual stimulation and a life free from persecution, finds new challenges in studying a different magical system and exploring a world that does not immediately want her dead. Zig, a pragmatic and highly capable fighter, must adjust his role from a soldier for hire in human conflicts to a guardian against monstrous beasts in a world where his usual services are obsolete. Together, the immortal witch and the mortal mercenary journey into the heart of this perilous frontier, seeking a place where Siasha can finally live in peace.