Do you know how mankind ends? Take up your weapon and fight back the monster invasion. The game that was boasted as the absolute hardest strategy game, [Isekai Defense]. I used to be the 'player' who had accomplished everything in this game and reached the true end, but it was a disastrous end where everyone died except the protagonist, Raon Eva. Determined to create a perfect happy end, I chose to transmigrate and found myself in the body of the protagonist as a child, surrounded by monsters in a burning village. With only my strength of will and memories of invasion as a player--. In order to save the people I love. I shall tear my enemies apart.