The Villainess’S Fifteen-Year War ~ Reincarnated In Pre-War Japan?! Avoiding The Doom Flags Won’T Be Enough At This Rate!! ~ (lightnovelstranslations.com)

A woman in her forties (unmarried, history buff) is reincarnated after the classic truck accident. She had reincarnated as a young girl with memories of her past life, but instead of a fantasy isekai world, she finds herself in "Pre-War Japan". At first, she thought it would be an easy life since she was reborn…