Cross-Dressing Villainess Cecilia Sylvie, Vol. 1 (manga)

Dearest Mama and Papa, Please forgive my disobedience. In order to evade my death flag, I, Cecilia Sylvie, have decided to become a boy! Cecilia has been reincarnated as the villainess of a dating sim who is fated to die no matter the route. If she becomes a Shrine Maiden candidate (only girls are chosen) like she does in the game, she'll absolutely wind up dead. No question about it. To avoid this fate, she decides to crossdress as a man... Cecilia will do whatever it takes to achieve a peaceful and carefree life, but if her guise ever slips, it's Game Over! Based on the light novel by Hiroro Akizakura!