Michika Nanase

One of the "Frown sisters". She never changes her expression.
A little sister who shows very little emotion. Her expression generally doesn't change.

She appears to love books as she's always seen walking around with one. Her room is filled with books.
She's a bookworm whose thoughts can't be read.
But if there's anything sexual going on, she goes after the protagonist relentlessly.
This is her way of expressing affection. Believing in the absurd information she read in a book that said, "In order to become lovers with the person you love, it's best to train your target," her aim is to make her older brother her own.

From what she learned in books, she's a skilled technician.