His face showed no sign of emotion, but inside, his heart was already pounding like a drum, and he was feeling extremely flustered, not at all as composed as he appeared on the surface.
Ever since he found out that Joanna was his lifesaver, he could never face her the same way as before.
He felt as if he had returned to the days of young love in his student years, and his heart would race whenever he saw the girl he liked.
The more he pretended to be indifferent on the surface, the more flustered he felt inside.
Because he didn't know how to face her, and because seeing her would make him especially flustered, his mind would go blank and he would be unable to think.
Because he was afraid of inadvertently saying or doing something wrong.
So he chose to not say anything and do nothing instead.