Asato Hitoha

Oldest sister of the family. Loves martial arts and training seemingly being super strong and athletic. Commands the most authority among the siblings including the protagonist despite being younger but seems to be old-fashioned and lacking common sense.

Spoiler

Was adopted at a young age, but she didn't know about it nor did her other siblings. The protagonist originally knew but forgot about it. Because of this she thinks she has most right to relationship.