The Setsu act... / changed... / Like this... /
She hadn't done things like to confront her "desire to monopolize big brother" to strangers before.
Onii-san, spread your legs a bit.
Here, say "haaa" / For sure... / Until before Setsu went on break for her exams...
In a way... One couldn't think that there had not been a change of heart
For example... / As if...
There was a special feeling that caused this desire to monopolize me... / I know