Kifujin Rosa wa Kage kara Ai wo Mimamoritai - Vol. 1 Ch. 1.3

[MangaDex]

 

[looc64]

Pretty sure "oshi" is slang for someone that you're a huuuuuuge fan of. Someone like an idol or a fictional character or something. Tbh I think that if you assumed that when MTL translations of Rosa's inner thoughts don't make sense it's because she's talking like a modern fujoshi you'd be correct. Like the conceit is that she's so "rotten" that she managed to come up with all those terms and tropes with zero exposure.

 

[KuroZer0]

I see her first victim.