Through an unexpected turn of events, Katsuki is being stalked by the creepiest girl in school, Endou. As a result, he's constantly on the receiving end of her "love" which, among other things, usually includes finding dozens of letters in his shoe locker and receiving creepy emails.

However one day, due to her obsessive nature, the two end up becoming closer when Endou forces herself on the short-statured Katsuki. Scared and reluctant at first, Katsuki soon becomes aware of his feelings towards her, and the two officially become a couple.

Stalking Girl follows Katsuki as he struggles to keep up with his new girlfriend's personality and whims.