An accidental trip by an alien brings the protagonist back to the past. As a reward, the protagonist is compensated with a cheating device. Low-key life, low-key development, digging pits, farming, mining, steelmaking, gunmaking, cannon casting, and aircraft missiles Add submarine torpedoes, use 21st century weapons to fight World War II. Killing people is fun, and destroying the sun is clean, but before that, we should keep our tails between our legs and be low-key.