Naruto System in One Piece - Chapter 484

Samuel, a high schooler, got summoned with his classmates to another world as prophesied heroes. He expected glory, adventure, and a chance to save a kingdom. But those hopes were shattered when he discovered the truth, they were sacrifices, the gods who summoned them are no saviors, but monsters that feed on human souls. Among the victims is his little sister, dragged into the summoning by accident while she was delivering his lunch. Betrayed and marked for sacrifice, Samuel survives andmade a deal with (Arithmos) the God of war, with its power, he now vows to destroy every god and declares to take everything from them.

This is the story of a modern sailor who was accidentally reborn as a soldier of the Brazilian Expeditionary Force, and finally became the largest plutocratic family in Brazil by virtue of his foresight.

- Description from novelbuddy

Usually when you possess a novel, you start in the city, but I fell into the forest.

“Everyone deserves a happy ending, don’t they?”…In the brutal fantasy RPG Fall of Ares, saving the world came at a cruel price — the deaths of every heroine the player had grown to love. No matter how skilled you were, their sacrifices were inevitable. The game warned you not to get attached.But one young man did.After beating the game and lamenting their tragic fates, he wakes up in its world — reborn as an extra, armed with one mission from a mysterious system:[Change their endings. Let them live.]Now enrolled at Mysteria Academy alongside the heroines doomed to die, he must rewrite fate itself. For every girl he saves, he’s rewarded. But the world resists change. Calamities draw closer. The true enemy — the Children of the Sky — are watching.And one of the heroines… remembers it all.