Akino Miya

The protagonist's older step-sister, who is one year older than hi,
She is the ultimate older sister who spoils the protagonist. She doesn't have much skills in most things, and relies on the MC to do the housework most of the time.
She is no-good at studying and exercise, and is a girl who fails at most of the things she does.
She doesn't have much to offer, but she is a hard-worker despite it all.
She is honest, gullible, and insensitive to many things. However, she sense that the MC is hiding something.