While usually Sonoko is unreliable, at the critical moment, her decisiveness,
judgment, and insight are the best out of the three.

Compared to her, when it counts, Sumi still hesitates.

Sumi finally understood that it wasn’t because of her family that Sonoko was
chosen to be captain, it was thanks to her own accomplishments.

Sumi felt a bit sick about herself for ignoring her own weakness, and blaming
her parentage for not being selected as captain.

(WaSuYu Chapter 3, 22)