That "Hmm?" did not express doubt; it conveyed a completely different attitude: it was your turn to switch.
In the beginning between boys and girls, the stakes were high. It was all about who would seize the initiative—from a strategic standpoint, a matter of getting the jump on the other person.
To seize that advantage, whoever made the first move would be at a disadvantage, and whoever grew impatient would lose the upper hand.
Chapter 505