i have gotten a story idea whilst playing romance detective 2 (1: https://nomnomnami.itch.io/romance-detective 2: https://nomnomnami.itch.io/romance-detective-2 , great plot, great games :D ANYWAYS-), and HERE IT IS CUS WHY NOTTT-
they might just stumble across a rose, or a substance of some sort, and decide to keep it (or consume the substance lmao), it does nothing at first but the more they see their crush, the more the rose's effects settle in. they may start getting weird messages and commands in their head when seeing or even being remotely near them. they eventually become full on obsessed, and the rose either takes full control, or it's done it's job, and left you to deal with your obsession alone.
(i definitely havent been reading simpbur fics, nope, why would i? totally not)