Runa is the new kid at school, so she's a bit confused about the whole "making friends" thing. I mean, who wouldn't be confused when the ceiling vents are haunted, her classmates are recreating the French revolution in the school bathrooms, and the student council is run by a power-hungry chuunibyou of 4-foot-2? Seriously, who put that kid in charge!
Completely against her will, Runa goes on an admirable (and whacky) quest to save Valentine's Day in the name of love. Or something else. She's not very keen on the whole idea.