Trying the remember manga with a ruthless mc
Setting: I think the main character is reincarnated into an otome game or just a game in general. He stops a plot with a woman who used charm on the princes of the country. Turns out later on, the woman was a prostitute who stole the ring of the heir of a noble family. She uses the ring to impersonate as that family's hidden heir and becomes a noble. Doing so, she gets the chance to meet with the princes/nobles and use charm on them. I don't remember how but the mc somehow solves the problem and the kingdom finds out about the women. She is then captured and executed, leading to mind control related magic becoming a sensitive topic. Fast forward a bit and the mc is in the academy. There is a girl who keeps stealing food from the cooking club. To counter this, the mc and friends make animal treats and puts a label for people not the eat them. The girl ignores it and takes it. She then gives it to various guys around the academy, leading to a mass outbreak of food poisoning. This puts her on the list as it is very similar as what the woman from before did. It is then showed that she actually idolized the woman and wanted to be like her, a princess with many princes. However the mc, who i thought was gonna kill her, brings her to the execution site of the woman and she witnessed the truth and the weight of her actions. This leads to her waking up her idea, and she leaves the academy to avoid getting prosecuted for the mass food poisoning.
I think it's a novel adapted into a manga