Hibikino Tsumugi

School Year: Sophomore
Occupation: Student, Accounting (and general affairs) at the Hibikino Shop

"That eroge releasing this month we've invested so much into promoting is... wait, delayed?!"

Of the Hibikino sisters, she's the most put together and takes care of managing the Hibikino Shop.
She still isn't pleased with how Yukari turned their home into an eroge shop, but now that it's a done deal she puts her all into the business.
It ends up that she does the most work of them all.

She's the same age and is in the class as the protagonist, having been friends from childhood.
They got along well back then, but after hitting puberty they've stopped interacting as much.