"Strain" is a science fiction manga series set in a dystopian future where humanity is engaged in a brutal war against an alien race known as the Ghoul. The story centers on Ralph Tykwell, a young soldier who enlists in the military to avenge the death of his sister, Lottie, who was killed during a Ghoul attack. Ralph becomes a pilot of a Strain, a powerful biomechanical weapon designed to combat the Ghoul threat. These Strains are symbiotic machines that bond with their pilots, granting them enhanced abilities but also posing significant physical and psychological risks.

The narrative explores the harsh realities of war, focusing on the psychological toll it takes on soldiers and the moral ambiguities of using advanced technology to fight an enemy that is both alien and enigmatic. Ralph's journey is marked by his struggle to reconcile his desire for vengeance with the growing realization that the war is far more complex than he initially believed. As he delves deeper into the conflict, he uncovers unsettling truths about the Ghoul, the origins of the Strain technology, and the true motivations of the human military leadership.

Key characters include Ralph's comrades-in-arms, such as Kikka, a fellow Strain pilot with a mysterious past, and Colonel Lottie, a high-ranking officer whose decisions often blur the line between duty and personal ambition. The Ghoul, initially portrayed as mindless invaders, are gradually revealed to possess their own culture and motivations, adding layers of complexity to the conflict. The series also examines themes of identity, loss, and the cost of survival in a world where humanity's existence hangs in the balance.

The plot is driven by intense battles, political intrigue, and the personal struggles of its characters, creating a tense and emotionally charged narrative. "Strain" combines action-packed sequences with introspective moments, offering a balanced exploration of its central themes. The manga's pacing and structure effectively build tension, culminating in a climactic resolution that challenges the characters' beliefs and leaves a lasting impact on their world.