Netherworld Investigator - Chapter 437

Mira is determined to be a botanist—no matter how dangerous or violent it may become. Mira made two requests upon entering the multiverse: a botany class to further her research and to be dropped off in an isolated forest far from the violent god-rearing system BS going on. She was granted both—but not in the way she expected. The system abandoned her in a hellishly dangerous forest—where she earned a rare class that excelled at killing things.

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

It was only after Su Yayan's death that she realized that she was a malicious cannon fodder female character who became a scapegoat in a Mary Sue story.