Kitai no Akujo, Sandome no Jinsei de "Musai Munou" wo Tanoshimu

Laviange, the first daughter of House Robur, is known for being disagreeable, irresponsible, talentless in magic, and utterly uneducated. Everyone believes she's completely incompetent—but is she really as useless as they say? The truth is far stranger. This is Laviange's third life. In her first, she was a legendary villainess and genius mage. In her second, she was an ordinary woman who lived to the age of 86—in Japan?! For her third life, she's decided to take it easy. Hiding her magical talent, she happily plays the part of an inept young noblewoman, enjoying the freedom it brings. But her carefree days come to an abrupt end when an outdoor training exercise goes horribly wrong. With the sense of an old lady and the power of an unstoppable mage, her accidental rampage turns her reputation on its head. The most hated girl in high society is about to become its most beloved?! The strongest villainess's riotous comedy begins! (Source: J-Novel Club)