Here's what might be a complicated idea but bear with me on it: a "sunshine noir" about a detective investigating a town that's been assimilated by a reality-warping spell (think the Hex from WandaVision), where upon entering it in order to find the source, he discovers the reality within has been bent to resemble that of a generic "cute girls doing cute things" slice-of-life anime. And by entering it, the detective becomes physically assimilated to resemble a female transfer student. She's able to retain her mind and plays along with the role in order to get closer to finding and stopping the source -- this Haruhi-style schoolgirl who doesn't realize she's a reality-warper -- but is constantly distracted by all the crappy comedy and cute fanservice happening around her and trying to not become fully overtaken by it.