Well... Midori's obsession with Akemi is romantic and lustful in nature.

But if her Shadow is an exaggeration it could take that vastly further and into more disturbing areas. From "I'll kill literally everyone but Akemi and I", even though Midori still loves her family and currently will only hurt people she thinks threaten her chances/love for Akemi(which will hopefully get better), or... well...

"Let's become one, Akemi-sempai! I have the needles and the thread here and everything!"

Or...

"I... want to be inside you, Akemi-sempai... [i]forever[/i]."

... Basically massively horrific disturbing things that would even freak Midori out. ^^;