Has My Sly Little Sister Already Recovered?

A story about everyday life between a brother and sister

His younger sister used to be a yandere, until one day he realized she had changed.

"Big bro, feed me~"

"What are you doing back here? Hmph, weren't you out having fun with a girl?"

"Stupid big brother is mine. I'm the only one allowed to call him stupid~"

His little sister seems to have turned into a tsundere...?