It has been half a year since Aini Mikkola, the saintess in training who hails from a barony in the countryside, arrived at the Royal Academy.

The school is in turmoil.

The boys, the sons of aristocrats, are at the mercy of Aini's innocent, natural cuteness, while the girls are angry at her disregard for the manners of the aristocracy. In the midst of all this, there were three daughters who were dubbed “the villainesses,” in reference to a popular story. Seraphina, the crown prince's fiancée and the daughter of an upright marquise. Sandra, the noble daughter of a viscount who made their wealth from commerce. Bernardetta, the brilliant daughter of the current Prime Minister's who is a marquise.

When a sense of disquiet begins to grow in the school, these women finally stand up! To correct Aini's mistakes and to follow their own hearts.

This is a record of the battle between the three “villainesses” and the saintly apprentices, a battle for the way of life of women.
折れない心＝メンタルつよつよヒロインたちの反撃！
王立学園に聖女見習いの田舎男爵の庶子アイニ・ミッコラがやってきて半年。学園は混乱の極みにあった。貴族子息である男子生徒たちはアイニの無邪気で天然な可愛らしさに翻弄される一方、女子生徒たちはアイニの貴族マナーを無視した振る舞いに憤りを覚えていたからである。そんな中、巷で流行の物語になぞらえて「悪役令嬢」と呼ばれることになった三人の令嬢がいた。王太子の婚約者で清廉な侯爵令嬢セラフィーナ。商売で裕福な子爵家の気高き令嬢サンドラ。現宰相の侯爵家の聡明な令嬢ベルナルデッタ。いつしか学園内に不穏な空気が漂い始めた時、彼女たちがついに立ち上がる! アイニの間違いを正し、自らの心のままに進むために。
これは三人の「悪役令嬢」たちと聖女見習いが繰り広げる、女たちの生き様をかけた戦いの記録である――。