A Commoner from a Poor Family

He transmigrated to ancient times without warning, to an era of war and unrest where people had neither clothes to cover themselves nor food to fill their stomachs. The population was dangerously low, so the authorities were forcing people into marriages to solve the problem. He was given a delicate bride, but he could barely support himself, let alone two people!

What? The enemy has invaded again? His wife trembled with fear, while the villagers formed a militia to defend their home. No problem. Master math and science, and you'll never be afraid anywhere in the world!

Steppe barbarians? Barbarians from across the sea? Send one, and he'll take them down. Send a pair, and he'll take them both down!