expression, godan verb (-su)
straighten oneself; compose oneself; take a serious attitude
Literally 'straighten one's collar', used figuratively for adjusting one's posture and adopting a more serious, attentive attitude. Often used when preparing to listen, speak, or face something important.
社長の話を聞くときは、襟を正して聞きなさい。
When listening to the president, straighten up and listen attentively.
He straightened himself and put on a serious expression.