Dekisokonai Reijou ni Tensei shita Gal ga Mikaesu Tame ni Doryoku Shita Kekka, Dekiai saretemasukedo nani ka Monku aru?出来損ない令嬢に転生したギャルが見返すために努力した結果、溺愛されてますけど何か文句ある？; I Reincarnated as a Useless Noble Lady

A modern day Japanese high school girl, Kirara, who lived her life as a so-called "gyaru", suddenly finds herself reincarnated as Chelsea, a "good-for-nothing noble lady" in another world. Unfamiliar with the rules of noble society and clueless about the usual tropes of isekai reincarnation, Kirara now Chelsea finds herself in a hopeless situation with no allies, thanks to the schemes of her younger sister, Jennifer. Even so, determined to turn things around, she takes action. She humbly seeks the guidance of a strict and well-known tutor and, using her natural grit and determination, overcomes the rigorous training. Chelseas reputation in high society begins to skyrocket! She even starts getting closer to Crown Prince Valentino and those around him...!?