Joshi Mousou Shoukougun - Pheromomania Syndrome(2002)

Joshi Mousou Shoukougun - Pheromomania Syndrome

Hatori is a tall girl who's easily mistaken for a boy, and she's in love with her childhood friend, Keishi. Even though he's a boy, Keishi is so cute that Hatori just wants to push him down and make him her own. Hatori has countless delusions and hallucinations (unbefitting a young lady) running wildly through her head every day -- and they're all about Keishi. They set her heart pounding and her nose bleeding!

(Source: Shoujomagic)