I forgot how unhinged the Persona 4 Visualives are.
Persona 4 Golden came out between the 1st and 2nd stage plays. So in the 2nd one, Evolution, the protagonist offers to make lunches for Adachi, similar to how he does in the Social Link. Adachi thinks this offer sounds "family-like" of the protagonist, and wonders if he's also going to be participating in the "you-know-what" at his upcoming school festival -- aka, the crossdressing pageant. Let's do the math here: In a typical family, it's the mom figure who cooks. This gets an insane reaction out of Dojima, who goes through 20 stages of [something] all at once, then storms off stage after declaring that he isn't going to trigger a romance event (恋愛イベント) with his nephew lmao.
Before identifying Adachi as the culprit, there's a whole montage where Signs of Love plays and the Investigation Team goes around Inaba. For the protag's part, he goes to the Velvet Room, gets the bug catching net from Margaret, then goes fishing. And then the play just cuts to the team at Junes, having called Adachi there, and they accuse him of being the culprit. I interpret this to mean, "A fish told the protag that Adachi did it".
