The Great Kang Blacksmith

Jin Feng, a modern man with a background in science and engineering, wakes up transmigrated into the body of a dirt-poor blacksmith in the ancient Great Kang Dynasty. They can barely afford to eat, and with the court running out of men, it has imposed forced marriages: "The government has assigned you a pretty wife. You must have a child by next year."

To make matters worse, cavalry from the borderland grasslands raid the south every year, while the Japanese pirates' ships are virtually indestructible. The whole village is in constant danger, and even basic meals are beyond the protagonist's reach.