Takatou Yui

Protagonist's blood-related little sister.

Though she has a diligent and serious personality, she is also good at keeping enough distance to not be too encroaching.

She worries about her sickly older brother, and genuinely adores him. But those feelings are solely those of siblings, not romantic feelings...or so she thought. With the arrival of Iori, another younger sister, those feelings gradually begin to show signs of changing...