i knew from the start that this murder recipe is a trap of some sort (it happened to be Youko's way to get closer to MC). There's no way reader wouldn't think about it. So from this scene I wasn't thinking what this recipe is about and all of this crap, but why she decided to show it to him.
the scene when the next day he was like "hey, looking for something?" - oh, so much cringe just for itself... And by the end "but when did you realized that I have this murder recipe?" - ooohhh, the cringiest cringe. You f**ing told her yourself, you idiot, so even if she really happened to lose this recipe by some misfortune, you just told her "hey, i've found something that belongs to you"
Kind of overpowered main female character. She is like some female Moriarty or whatever. Hahaha, it was planned all along! - kinda like that, but without "hahaha, it was planned all along" actual line